I have used two different systems to clamp the actual Pan I'm hammering on onto the Rotating Base. This one is the easiest to make.
The Miniclamps are made from 3 components.
The Inside Piece is a 2" x 2" square of 3/4" plywood. It has two "legs" that are 3/4" square pine, about 4 inches long. These are screwed and glued onto the edge of the square. There is a 1/4-20 threaded insert in the middle of the square.
The Outside Piece is a 2" x 2" square of 3/4" plywood with a 5/16" hole drilled through it
The bolt is a 2" long 1/4-20 Stainless or High-Tensile bolt. Regular bolts wear out fairly quickly.
The purpose of the 3/4" square pine blocks is to keep the threaded insert away from the edge of the pan. The threaded inserts are approximately 3/4" long, and so they stand proud of the 3/4" thick plywood; this can cause the clamp to not tighten properly against the steel.