The first step is to gather the materials you'll need to make your Christmas tree napkin. You'll need a square or rectangular napkin, a small piece of cardboard or a paper plate, and some tape or glue. Next, fold the napkin in half diagonally to create a triangle. Then, fold the napkin in half again to create a smaller triangle. Fold the napkin in half one more time to create a very small triangle. Finally, use the cardboard or paper plate as a base and tape or glue the napkin to it. You'll now have a lovely Christmas tree napkin!