Summary

Use M3x4 screws to secure the board to the tray. You may have trouble threading some of the screws. It will be easier if you do that before installing the board. Out of the 6, I had one stubborn screw that required heating a bit with hot air to make it go in. If you have a lot of trouble with one, just heat it up to around 90-100C and push it in a little bit. Not all the way. Once it's cooled you'll be able to tighten it and it will hold well.