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
Artist Erin LaRocque (of BuildWithWood) creates beautiful pendants by encapsulating natural treasures, found in Michigan’s Hiawatha National Forest, in resin and laser-cut wood frames. This would be a great way to preserve vestiges of felled forests.