Thanks all! The ruins have been great fun to do- as OldSchoolSoviet points out, the swirly water effect on the webway gate isn't as good as I'd like it, but I'd literally painted myself into a corner there- really I should have done the whole gate as a single piece and then attached it to the base, but instead I added the effect last, when it was incredibly difficult to access thanks to all the flowers, models and other stuff around it. A failure in planning there.
So, you may be wondering what I'm planning on doing next. Well, the Gorilla Bots need to be finished, and as they are currently sitting in the painting queue, I felt it was time for me to get on with their scenic base. You've seen some of the accoutrements, but not the thing itself, which has now come on a fair bit.
In choosing the theme, I was conscious that I wanted to do something different that I hadn't tried before, but would also be a challenge. I did wonder about an icy base, but then I had a brainwave- they'll be in a Mangrove- themed situation, which is not something I've ever seen anyone attempt before. This is what's led to the idol, the savage ratlings, etc. The plan was to have a section of beach, an expanse of water and mangrove trees on either side; the robots and their master would be on the shorline reacting to the appearance of xenos in the water. Or at least that's the plan... here's how I started to go about it!
Firstly, I went to the shops and bought a plastic flower pot thing and some sand. As you can see from the price tages, this was expensive stuff!

With that ready, I then started planning. This basically meant drawing on the pot to deliniate what went where.

Having decided that there would be one area with a single tree and another on the other side with more than one, my next job was to make the base bits, so I could fit them and make sure there was enough space.
Leaving the flower pot to one side, I started off by getting some wire and twisting it together. This forms the basic roots, trunk and branches. As it's a mangrove tree and the roots are exposed, they need to be done too. I ended up with this, which I then secured in place with a bit of superglue...

The next step was to start giving the branches some body. To start off with for this I got some matte acrylic gel; this will allow me to bend the finished branches and roots around without everything cracking and will also give the final texturing something to grip on. Five minutes of application with a toothpick later, and...

Once that had dried, I then needed to add the real body. For this I used some wood filler, which is a bit heavier-bodied and more flexible than normal polyfiller, and also dries with a nice texture to it. Taking a spoonfull of filler out of the pot, I mixed it with a little water and some brown paint, then added it the same way as I did the matt gel. The result is a bit blurry, but I hope you get the idea...

Still lots to do here, of course- it needs more than a base coat on there to look properly woody, and most obviously the foliage has to be added. But it gives a sense of the thing's footprint, which is all I need for the moment.
The next step is to actually get some relief in the base. This is particularly important as large chunks of this one are meant to be underwater. As you might have seen with previous projects, I've tried various things to achieve this relief before; plaster, polyfiller, papier mache, and so on; after a fair bit of experimentation, I've come to the conclusion that for something that needs lots of control and is on a large scale, air-drying clay is the best bet.
So that's what I've gone for here! Splodging some clay into the first area earmarked for trees, I got it to the point I wanted (I'm using the first ridge on the base as the rough target point for the water level, putting all of this underwater), plonked the tree on there for comparison purposes and then, using the same wire as I had for the trunk, added a whole load of new roots coming in and out of the ground around the tree.

This took quite some time to dry- one of the issues with DAS clay- but once it was done, I gave each of the roots a coating of the matte gel so they would end up with the same wood effect as the tree.
Gradually, I went around the whole base doing this- adding layers of clay, letting them dry, and then building them up further if neccesary. When the other trees, altar etc went on, this is what it looked like;

You'll notice various bits placed on the base too- I'll get to those. Once everything had dried, things were looking a lot more complete; but a lot needed to be done before I could progress. One of the downsides of using air-drying clay is that it's not waterproof- it also shirnks slightly as it solidifies, which means that in combination with a flexible plastic like the flower pot, you can end up with cracks and gaps. There are several problems with this; firstly, the clay isn't really attached to the base securely, and secondly, if I were to pour water into the thing to check how much resin I'll need for the final run, it would soak the whole thing. Even if that wasn't a problem, the gaps between the different layers of clay and the plastic base risked me wasting massive quantities of the water-effect resin as it seeped in between them.
To prevent this from being an issue, I needed to seal everything. The first step in doing this was a coat of the matt gel over all the clay, paying particular attention to the gaps between the clay and everything else. This should also smooth the topography slightly, making it easier for the sand to get some grip and making everything look a little more realistic.

And that's where I currently am. More soon, I hope!