As per the original author.

"Designed to fit standard 8.5mm square buttons.

Added 2 sets of mounting screw holes so it can be mounted with the buttons facing out or up or just use double sided tape.

The buttons are an exact fit in the holder to avoid movement but will require securing in place (small amount of hot glue on the back is perfect). The LED's are a snug fit once pushed through the holes and will hold in place themselves (hot glue can always be used if you think they might come out)"

Additional this was entirely made in Prusaslicer and I have zero design skills, so it's not perfect.. specially the countersunk part!