My workshop.
You need a good cutting mat, burnishing roller and utility knife plus a sample roll of Seal Print Mount ultra.
Cut a rough 9x12 piece of Ultra lay your print on the sticky surface and burnish it down. On the backside of course.
Flip your print face down and trim it to the edges. Can take a little practice.
Take your backing board and either make a jig or put really fine pencil points in the centered area where you want it.
Pull an inch off of your backer and line your print up with your marks.
Press that area down first then slowly pull your backer completely off. Burnish your print down and done.
If you lined it up with care it should be on straight.