I found a blog post concerning Warmachine model base improvements; the modeler created a wooden floor design using clay. Believing that Sculpey polymer would do the trick, I created rock piles for the Protectorate of Menoth figure bases in our starter box.
Unfortunately, I learned that the 275 F baking temperature exceeded the melting point for the bases, ruining them. I guess the other modeler used an air dry clay or other base material.
Fortunately, I didn't try this with the Warcaster figure that is already glued to the base! I did salvage the baked rocks, which will be applied to unmelted bases or a terrain feature.