If you don't have a circle punch, trace the magnets on the scrapbook paper and cut out with scissors.
Paint Mod Podge on the back of the marble piece and on top of the paper with a brush.
Gently place the scrapbook paper on top and press down. Set aside. Repeat with the remaining marbles and paper. Let dry for 20 minutes.
Trim the excess paper around the edges using scissors.
Add a dab of strong craft glue or E-6000 to the back, then firmly press on your magnet. Repeat. Let your magnets dry for several hours before using or gifting.
Video
Notes
There are kits available on Amazon with adhesive magnets that allow you to skip one of the gluing steps. Find them here.