Preparation

TemplatePrinter and paperTranslucent paperSmall LED lightDouble-sided tape

Download and print the template.Take the print to a copy center and enlarge it to whatever size you want.Trace the pattern onto translucent paper, and cut and fold where indicated.Place a small LED light inside, and use double-sided tape to secure. Voilà! Everything is illuminated.

“Pergamenata” 160-gram paper (for geodes), $6/sheet; nycentralart.com. Submersible LED lights, $16 for 6; skylanterns.us.