Make sure your oven is preheated to 200° The first thing you want to do, is mix the flour, salt and warm water in a bowl. You can use a spoon at first, but once it gets mixed in good, you can start using your hands to mix it up if you'd like. I find this easier.
Once it is all mixed up you can make them into round balls. You can also use a rolling pin to flatten the dough and cut out shapes if you'd like. I just rolled them up into a ball and pressed down on them to get them flatter. I find this to work easier for me and it looks more real this way too.
Now you can start using your plastic reptiles to press down on the dough to create the fossil look. Use whichever ones you'd like. I used a package of plastic reptiles, but use whatever kind you want or have around.
Now make sure your parchment paper is laid out on your pans. Then put all your pieces on the pan once you've pressed them all with the plastic reptiles. Put them in the oven for about 2 hours and they should harden. You might need more time depending on the thickness of them. Mine only took 2 hours.
