Carry the double check even further and make the slip a mini sign off. Write the fat cap choice, the weight, and the date, then have the customer put their initials right next to it before it hits the smoker. It takes ten seconds and stops the whole "you should've trimmed it" thing cold, since nobody can argue with their own handwriting. A phone pic of the slip stapled to the ticket helps too if they get loud about it later.

My wife showed me the corner tuck thing about 3 years ago and I honestly felt dumb for not figuring it out sooner. The part that finally clicked for me was doing it on the bed itself instead of trying to hold the whole sheet up in the air. Lay it flat, tuck the corners inside each other so you get one neat stack, then fold the sides in and it turns into a normal rectangle. Takes me maybe 30 seconds now when before it was a 10 minute fight. The elastic never fights back once those corners are nested.