A paper template was made for the 0.25" birch inserts. The template was traced onto a scrap piece of birch plywood. A pilot hole was drilled into the location where the 3/8" hole is to be drilled and 3 additional pilot holes were drilled so that nails could be used to hold 2 pieces of birch plywood together so that they can be cut at the same time to make identical inserts.
A 3/8" hole was drilled through both pieces of plywood using the drill press.
The inserts were cut to size using the band saw and then sanded.