Kobold Lair

Thi is a more challenging encounter to develop. The kobold's serve the dragon within its lair. The dragon clearly has no real need for them, they only serve to bloat its ego. I suppose they also amuse the dragon, as well. As such, the kobold lair is a separate location from the lair, even though they are connected.

The dragon lair also has lair effects that impact the surrounding countryside. These can be felt in the mountains around the kobold lair. This complicates this area, encounter-wise. The kobold lair needs to be developed, the dragon lair needs to be developed, and the lair effects structured in some fashion to allow their easy use. Then, all three need to be balanced with and against each other. This is a complicated endeavor.

I'm not sure what the best method is. I think in real terms it will mean developing them one at a time, and refining each as others get going. That probably means several attempts at each of these with a final smoothing necessary in the end.

In terms of game play, my plan for the kobolds is to develop a busy maze of tunnels that will present challenges to players in terms of traps, dead ends, etc. My thought (with a party of 8th or higher level characters, kobolds aren't much challenge in a fight) is to have a warren of tunnels that the party needs to navigate stealthily. The intent to avoid combat, and thus to avoid alerting the entire clan and the dragon to the party's entrance.

The kobold lair is an entry point to the dragon lair that is relatively "unguarded." They can get to the dragon directly in its lair with an element of surprise by moving through the kobolds. This could allow them to get close, or even approach the dragon's lair when it is out, allowing them to set a defense to spring when it returns. A lot of this hinges on getting past the kobolds without raising much of an alarm.

Dragon Cult

The dragon cult has a well fortified hold in the mountains north of the volcano. They have been searching for something.
This is a rough sketch to get started on a general layout. The slaad have information on the geography, the location of the two main guard outposts on the left outcropping and the main spur of the mountain. They aren't aware of the guard on the eastern spur.
They also know of a patrol on the northwestern slopes, and along the valley floor around the main keep. There is another patrol in the higher reaches of the main spur that they never detected. It is a high patrol, and observes more than interacts. They have magical means of communicating directly with the innermost circle of guards. If they see anyone coming, they will alert them, but not give any other warning.
This helps the leaders demonstrate greater power, by "sensing" the approach of intruders even before the guards or patrols notice. If the party specifically mention taking a high pass approach to the outpost, they can spot the secret patrol on a Perception (DC22) check. Any similar action looking for someone while high on the spur gets the same roll.

Information

What do the slaad know of the cultists or the kobolds? Excellent question. The power of the volcano calls to the slaad, and draws them to its heart. Because of this, they frequently visit the feet of the volcano, searching for entrance, and probing every hole or crevice in an effort to find a way in.
They fear the dragon, but little else, and visit in the night to learn its secrets. They have discovered the entrance to the kobold lair, and begun gathering info about their coming and going, looking for a way to exploit it.
The cultists are further away, but many of the slaad passed near it following the call to the portal in their village. Their journey gave them a good view of the location (otherwise unknown), layout of the approach (including guard locations), and a sense of movement (including patrols). Their knowledge of it is passive, though, garnered from shared observation that is increasingly outdated. It should be enough to arouse the players' interest, and suggest they visit before going to the lair itself.
If the party fight the slaad instead of communicating with them, this information can be found in the green slaad chief's hut in the form of crude maps and sketchy info. He was gathering information for the giants, who had begun taking an interest in the movement of the dragon cult, and its connection with the kobolds serving the dragon, as well as the dragon itself.
There is also a cryptic reference to something at the cult location that is being prepared for the dragon. What that is can't be discovered from the slaad, but should encourage the party to explore further. There is no map of a trail leading out of the swamp, only a direction of travel for each location. Actual inspection outside of the village will reveal a path leading toward the swamp's edge, but more toward the mountain and the entrance to the kobold lair.

Slaad Motivation

The slaad have been drawn to this location because of the portal to Limbo opened by the chaotic thermal energy generated by the volcanic flows beneath the swamp. Something about it resonates within the control stone lodged in their skulls, drawing them to this spot to commune with the portal.Coming from several locations, they have amassed a great deal of information about the creatures of the surrounding area. Most notably, they know the location of the dragon cultists, and the entrance to the kobold lair. As a rule, they prefer to devour and infect their prey rather than communicate with them, so this presents an obstacle to overcome. Possessing the control gem, the party can direct the actions of the head of the green slaadi. If a fight breaks out, they can still control the green slaad's actions, but they won't be able to glean specific information about the cultists or the kobolds.
There is still a chance for them to gain partial info about both by searching the hut of the green chief.

Slaad Village

The slaad village is set up with a color heirarchy. There are circular paths leading to small clusters of huts that wind around the base of an upthrust spur of lava, eroded on either side. There are blue huts in the lowest areas of the swamp. As the trail through the village climbs up higher, the huts become more substantial and house red slaad.
On the rough lower slopes, there are a cluster of green slaad huts. The exposed lava tube rising above them is wound round with a rough trail leading to a dwelling built into tube itself.
The path the party has followed leads in a sweeping turn into a cluster of buildings. There are roads curling off to the right and left, each looping into itself with huts lining them. At the center of each cluster is a principal "family hut" of larger size. The huts get more substantial with the evolutionary cycles.
There is a second peak beyond the Grey Slaad's hut that is sacred to the village. It is a portal to the plane of Limbo, and can be used to summon a Death Slaad. The Grey Slaad will sacrifice a green slaad to open the portal (there is a 20% chance the green slaad will turn on the grey and try to sacrifice him in order to usurp his position.
The green slaad chief had the stone in its head taken by a cultist some time ago. They turned it over to the fire giants. It is the stone that the players have recovered and been carrying. The green stone gives the holder control over the green slaad chief. Without an Arcana or Nature check (DC20), they will not realize its power unless an occasion arises in battle where it will obey them.

Pause

I haven't been very diligent about keeping this up and full of useful information over the last two months. Partly, it is a result of spending a lot of time playing games. This is great for me, but detrimental to this effort. Ultimately, this is a way to keep thinking about D&D and actively creating content to offset not being able to actually play on a regular basis. It is meant to generate interest, inspire creativity, and spread the game while being creative internally. I like doing it, and want to do it right, but lately, the options have been there to actually play more.
Not always D&D, but enough opportunities to play games to distract me from this. I still care about this and try to contribute, but I'm not giving it the proper attention, and it is suffering. The answer is simple - start giving it the attention it deserves. The solution is not so simple - it means taking time from playing games to build games, it means finding some other thing to scale back to make up the time needed for giving it proper attention. It is difficult.
I think in the end, the real trouble with this is that I've lost my way. I'm not sure where I am with the adventure anymore, and I have no clue what I want next. I have vague general ideas that have been with me since the outset, but that I always managed to push away to the indefinite future (which I've caught up to now). I probably need to step away from this for a while to let it gel, then build a proper finale.
That means that I should shift my focus here onto something else, something more manageable and interesting to me at this time, until inspiration brings me back to the main story. I think I've met the initial challenge for myself anyway, to build an adventure from scratch on a daily basis, giving insight along the way into what I'm doing, how I'm doing it, and so forth. It was a challenge to myself to develop it, and a challenge in the form to deliver it. I think both are well served.
I think there are still three major plot points to resolve prior to engaging the dragon in its lair, as well as one minor thread in tangent. These are the encounters with the slaad village in the swamp (the green stone is a controlling stone for one of the slaadi, probably one in cahoots with the giants, but about what??), a major confrontation with the dragon cultists at their primary shrine in the mountains, and the journey through the kobold lair in the volcano's base, the back door to the dragon's lair. The minor thread is the experience around the volcano caused by the lair effects of the dragon's presence.
The drawback to these is that (in the first two cases, at least) they are involved mini-adventure paths themselves. They almost need to be built independently of the whole, then merged. That is a little tricky.
I think I'm taking a break to explore some other elements of dungeoncraft and gameplay, but fully intend to complete the adventure, hopefully soon.

Giving it Thought (sort of)

I don't think the party needs to face the entire lizardfolk clan or village. It should be enough to run across small bands. They could be scouts or other patrol groups of 3-5. These feature pretty generic creatures.
There could also be more substantial patrols, with shaman as well as the usual. Even coming in larger numbers. I think the smaller groups would be in ambush, and setting traps. The larger groups are more traditional patrols, with more muscle and less stealth.
The slaad should just be in groups of 1 or 2 for now. I need to get a better handle on the colors before saying much about them.
If I remember rightly the party is 8th level. This means that lizardfolk aren't a particularly deadly challenge on their own. More numbers could boost that, as could incorporating some creative traps.