I like to make my owm foam plugs from flip flop sandels, using sharpened brass tubes in a drill press. After reviewing other posts I thought I would pass along a tip that I found to speed up production.

I start by cutting out a rectangular blank from the sandel, usually 2-3 inches square with a depth a little over the final plug length. I the set the drill press depth to cut within 1/16" of the bottom of the foam. I then cut a series of plugs in a tight pattern over the entire surface. The plugs stay in the foam blank and I don't need to stop the press to eject them. When finished with the drilling I release the plugs by slicing a 1/16" off the bottom of the blank with a sharp knife or band saw.