here's another good base material. It's sorta like Critr Gitr's idea. Only I by the used bases and plaques sold at craft stores and the like. just sand, stain, sand stain, sand, stain, and you're done....really it's not that much work. you probably only need to sand and stain it once or twice, just to smooth it out and give it some color and sheen.
in fact the rougher the surface is where you're attaching the base, the better. gives it something to stick to.
BY THE WAY Ryan- another good glue for attaching bases is construction glue, like Liquid Nails. doesn't dissolve the insulation board, and once its dry, it'll hold like nothing else.
-gringe88