Hey guys, I use a marble 12 x 12 floor tile. Stays colder than room temp and have never had a problem with clay being too soft. Also, I never bake the clay. I find with pop molds it causes damage to the edges when trying to remove the blank. I simply make my mold box on the piece of tile, pour the pop and let it setup for 2 hrs. Then remove from box and pick out the clay. I've been using the same piece of clay for all my molds.