Here's the mold. I'm far too impatient for brush-on molding so a block mold it is.
I had originally intended to cast these out of rigid foam, which ended up disastrously, so I decided on just casting them out of resin with a hollowed out back to keep the cost and weight down as much as I could.
Again, I could brush in the resin or slush-cast, but I just wanted these to be as quick and easy to produce as possible so I opted to make it hollow by way of dispersion with a plaster form, or rather, lower a form into the liquid resin, displacing the resin to fill the entire mold up to the rim. I simply lined the interior of the mold with at least 1/2" thick layer of Monster Clay (this would later represent the actual final casting). Once done, I made a wooden bracket with screws attached with the ends fitted with washers to hold the plaster displacer in. Then I poured the plaster.
Once cured solid I pull it out and I get this...
This displacer form will get sanded super smooth to keep it from sticking to the resin during casting. Following the very good suggestion of a Smooth-On technician, I covered the entire form in a nice thick coat of Vaseline, and took some plastic cling wrap and covered it (which will make demolding far easier). Forgive the lack of pictures showing this step but I just don't have any. I then smooth the wrinkles of the cling wrap with my fingers covered in Vaseline and top it with a light coat of mold release.
The result is a quick and easy hollow casting. Add a gator teeth picture hanger on the back and you got a wall bust.
