Check out info on resin casting. You have a mold, mix the resin with a catalyst. Whatever is in the mold gets embedded in plastic. - This link doesn't include info, but it's a reminder to go check out more info on resin casting
Fun project to do with the kids! Melted bead suncatchers - *Layer cheap plastic beads in cake pans (no lining required), melt at 400 degrees for 20 minutes. Let cool & then flip them out. Drill a hole in it to make it a suncatcher.