I began by making the pits, since they seemed like they would be the easiest. I began with some 1.5" fender washers, first gluing a bit of paper over the hole in the center. I then used some greenstuff to build up a rim around the outer edge. When the greenstuff was dry, I sprayed the pits black, and then painted them with shades of brown, leaving a bit of black in the center to give the illusion of depth.
For the Earthen Walls, I cut the basic 3"x2"x1" shape from some scrap pink insulation foam, and carved it to give it a rough appearance as a pile of dirt might have. I then glued it to a 3"x1.5" steel base. When the glue was dry, I painted the walls with a paint and sand mixture to give it some texture, and then sprayed the walls with some Flat Dark Brown camo spray paint. When dry, I drybrushed some lighter browns over the surface.
For the Pool spell, I took some CDs, and cut them down a little to give them an uneven outline. I then cut some 3" circles from some heavy paper.
When the "Water Effects" dried it gave the nice illusion of water in the pools.
I'm really happy with how these turned out, and they really helped add to the look of our convention games!