My boys have been dinosaur OBSESSED lately, so they were ecstatic when I told them we were going to make our own "fossils." I bought 2 small packs of Crayola Model Magic for this project. We'd never used it before, and I discovered that it's pretty awesome. It's nice and soft, and not nearly as messy as Play-doh.
They took small pieces of the Model Magic, flattened them out somewhat, and then pressed plastic dinosaurs into them.
My oldest, A, made several "fossils" and then set them aside to dry out. K, however, played with his clump of Model Magic for about an hour! He did not really care about having a finished product, he just wanted to play. He went back to it last night and this morning as well. That is fine with me! He also came up with the idea to make dinosaur footprints in the Model Magic, which you can see in the first picture.