I needed “side clamps” to fix the item on a CNC Table. So I inserted M6 Nuts into the underlying wood and fix the item with adjustable clamps:

3 parts needed for each clamp:

           Arm with rim fixed with M6 Screw
           Ramp to adjust the high of the Item
           Adapter to connect Arm with ramp.

Additional I used a washer and 2 nuts per clamp.

This works fine for me also for bumpy surfaces.