The circle is perfectly sized for the M5 sized threaded inserts with a 6.35mm mounting hole. Just press them into the hole.
I sanded an angled edge onto my clamps to give them a lower profile for the part of the clamp that is over the material. This makes it easier to avoid hitting the bit against the clamp.
Each clamp uses 2 screws, one in the threaded insert and one which goes into the threaded inserts in the wasteboard.