Having just went through the process of doing a few custom wrist rests like this over the last few days, it's not worth sealing up until you're sure that you've gotten the ergonomics right.

Far better to work quickly & test it out for a few days first to see if the angle / height / depth are off at all.

My kids wound up with new wrist rests on their keyboards after I realized from an initial attempt that I really needed at least 4" of depth.