Basically, just copied from the plan, using a circle stencil to scribe the ends. You note two marked tabs for the front plate and no tabs for the rear. I actually used one for each.
The clamp draws the plug into the slot, shaping the brass. While this worked, it didn’t work very well. I bent the screw on the form clamp and the back is curved in the vertical plane, which made fitting the infill extra painful.