- A piece of regular copy paper cut to size can be attached using a temporary adhesive. If any adhesive sticks you can use an adhesive eraser to gently remove it.
- Use Post-It notes to cover the center while you're stamping.
Either of these methods work fairly well. You can use whichever you have on hand. I happen to like the look of background printing, so I'll probably continue to do that as I finish my calendar.