Brad, Sculpey can be a tricky medium to work with. If I need to add a second layer that is fairly thick I prepare the first layer by rough sanding it. I then take some Sculpey diluent (the liquid stuff that comes in a little bottle that brings old sculpey to life) and rub it all over the first layer. When you add additional layers and then bake them they should bond really well. It's typical for sculpey to crack or fracture if you carve into another layer, it has happened to me several times. It a matter of learning the medium.~Gary