Im currently in the process of creating props and i thought i would share my process.
A lot of people use worbla or eva foam, which ive used both before. there's nothing wrong with either and there are tons of tutorials but I wanted to try something different this time around.
I'm using something called poly plastic. Which are pretty much just plastic beads.
Instead of melting these down via a double boiler im actually doing a mixture of equal parts of the beads and flour and baking it. (1/2 cup beads, 1/2 cup flour).
once it is melted, i roll it out like dough