I agree with Bert that there shouldn't be a need to put down the release paper if you put on a finish first. Most likely that would be a waste of your time.

Besides less effort, I think a wood ornament with a nice subtle bit of finish will look better than raw plywood, but that is just my opinion.

Release paper doesn't always adhere really well to plywood. Get something with a good strong tack and really roll it well to get it to adhere. Start lasering as soon as you are done applying the release paper to minimize the chance of the paper not sticking for long.