I have been using Celluclay as the "Base Application" on my dioramas for decades .... And it works for me. Below are some pics of this method, I will be glad to answer any questions you may have. Thanks for looking.

Hi, Dave!
I mentioned in your other thread about Celluclay, that I add a little white glue to the mix. I found it helps keep the edges from cracking or lifting, especially if the material is thinner at the edges. Do you use this technique, too?

Prost!
Brad

Good point Brad - I also mix in a dollop of white glue when mixing celluclay and don't normally experience any problems with it lifting at the edges.