Freeze your cakes before you sculpt. I take the cakes from the pan, let them cool on a rack while cleaning out the cake pans, then place a sheet of waxed paper in the pan, followed by the cake, which I then cover in the waxed paper (like a blanket), place back in the pan, wrap the entire pan in more waxed paper and plastic wrap, then place in the freezer.
This guy is sorta plump and chunky looking for a dinosaur. I usually place spikes down dino's backside, but this time was requested to leave him bare.
