by Mike - Alumilite » Mon Mar 05, 2012 7:56 am
I'm not an artist but I'd try sculpting it to make sure it fits the bottom perfectly. There are enough on the market that you could look at to give you an idea of where you want your's to go. Sculpey is an extremely easy polymer clay to use. Once you've sculpted your piece, simply bake it for 15 minutes and hit hardens up. Then, if need be, you can sand it perfect and pour your mold. This will allow you to get the perfect thickness you desire of your frog and make sure it will fit precisely to the bottom.
Mike