It's not difficult to do and you don't need a guide, all you need is a glass hole saw and a drill with a clutch. I used some thicker cardboard with holes the size I needed cut out and taped around the edges. I then poured water into the holes and kept adding water as I cut. The cardboard is only there to keep the hole saw in place until it starts to cut, after that it will sit in the groove. Adjust the clutch to a lower setting so that if the drill binds the torque won't break the glass. Just go slow, keep the drill level, and keep adding water to cool and your good to go.