My 4x5 pinhole camera is made of strawboard (similar to MDF, but made of compressed Canadian straw). I use a 1/4-20 T-nut with a counterbore for the flange inside the box. I also discovered that a US penny slips perfectly into the required 3/4 inch counterbore on top of the T-nut flange to stop light leaking through the T-nut thread hole. Cheap, effective, removable if needed.

Lee