Do it yourself

Hello, I put a bay window in earlier this summer and I'm trying to figure out how to "dress off" the bottom outside portion of it. It comes out of the side of the house 14 inches, and I would like to build a "fake" wall from the bottom of the window straight to the ground. Then face that with the fake rock ( man made cement rocks ) facing. In doing that do I need to pour any kind of a cement pad for the interior of the fake wall? ( we live in Michigan, so frost may come into consideration ). If now, how do I keep critters from burrowing underneath the wood to ground and making nest and such? I would also like in insulate that wall, since it is an outside wall, I suppose it would make the window seat warmer. Please, any thoughts or direction would be great - Denise