Same linkie as in the other thread.
Assuming you have adhesive-backed magnetic sheet (as opposed to the roadside junk I used):
- Cover the other (“refrigerator”) side of the sheet with blue tape
- Inset the graphic shape by a few millimeters
- Cut the magnet, clean the edge, peel the tape
- Cut the graphic as you usually do
- Peel-n-stick magnet to graphic
If the magnets (or the graphics) aren’t PSA, then cut a magnet-sized piece of adhesive sheet and add it to the stack.