Making Holes In Cubes

Hello. I am making something in blender to have it 3d printed. It is going to be mounted to a wall, so I need to put some holes for screws, preferably countersunk, in the back plate (made with a cube). If anybody could tell me how to do this, I would appreciate it. Thank You. :slight_smile:

Check out this answer, it explains how to cut holes in a mesh: