You can buy the foam forms in different sizes from any of the taxidermy supply companies, Mckenzie, Research Mannikans, etc... They all have a large size for elk antlers, $8-9 for on form. They also have replacement skull caps you can attach sheds to. Just drill 4 holes in the skull cap, srew into the plywood on the foam form, get some paper mache' and fill in the gaps around the skull cap. Then follow what Backpack Hunter said with covering it. If you use leather, make sure it is soft enough to work and stretch, don't use the thick leather they use for some crafts and stuff, not plyable enough.