All I do is set a can of Super777 spray glue on my kitchen floor, turn on all the lights to make it as close to full sun as possible.
Then I hold my quad about 4-5 feet away and focus the camera to be able to read the most I can off the label.
Then I lock down the ring as best I can and dab some hot glue between the lens back side, over the ring, and on to the case.
It usually wont stay on but I manage to get a few weeks of bashing in before refocusing is needed.