Made a bunch of resin plinths the other day. Used PVC pipe fittings as the mold and it worked well. Even has a little indention in the top so your groundworks can be level with the top of the plinth instead of spilling over the side, getting the paint rubbed off every time someone picks up the piece. The trick is making a little jig so you can safely and evenly trim the bottom edges off, give it a nice curve on the router table. Other than that it’s super simple. They have a #8 t-nut fixed to the bottom so they screw in to my transport boxes securely.