each hole switch sits in a cutout area on the top side of the hole. If you don't have the switch assemblies or you remove them, you'll have a recessed area in the back side of the playfield and a notch that light will can come thru to get indirect illumination of the hole.

you'll also have 8 holes where the playfield lights are mounted ... the white things with the red tops ... and if it's just the plywood, a big hole under where the red cap is.

The holes are around 1-1/4" in diameter. You'll need something inside or behind the holes unless you want to see what's on the wall behind where you hang it.