Not sure if it’s been deemed kosher or not, but I smear mine with clear silicone. I carefully affix the plate with painter’s blue tape. I let it sit for 24 hours, weighted. The next day it’s ready to drill. Seems to work just fine.
If the panel is pre-drilled, the washers from the footswitches and potentiometers will hold it snugly in place. You can still add adhesive if you’d like (E6000 or similar), but it’s not required.
If you’re drilling the panel over the enclosure, then you must use silicone or a similar adhesive and let it set as outlined in the official guide.