I found some nice 1/4-20 machine screws to secure my wasteboard to my CNC table top. I’m using flanged, threaded inserts installed from the bottom side of the 3/4" MDF table top. While searching for low profile fasteners with a wide head (to help prevent pull through), I found these sidewalk bolts from Hillman on Amazon. They are stainless steel with both a slotted and philips head. Head diameter is right at 0.750" and the head thickness is approximately 0.115. Countersink holes at 0.800" diameter and 0.325 deep worked great with these fasteners. Only $27 for 100 at 1-1/4" long.