base material for celluclay

I always use a wooden base with holes drillied into it to increase bite. I don't hink Celluclay will adhere to a non-pourous surface (glass/plastic, etc.) since its glue is water based.

That said, you should build up any significant terrain with styrofoam, either sheets cut from blocks you buy or from leftover electronics packaging. Still, these won't adhere well to non-pourous surfaces.

I use plastic box photo-frames... I just rough up the surface with some 80-grit to give the Celluclay something to stick to...

I prefer those because I can glue them together to create any size base I need, they're cheap & easy to cut hole in for foxholes, ruts, etc, and they're hollow underneath for securing the models with nuts & bolts and can also hide electronics, if any..

I have had issues with the Celluclay lifting now & then due to warping of the wood trim around it, but a dollop of glue and a C-clamp fixes it pretty easy..