These are super easy and fun to make and decorate. If we had time and space, we would make a whole forest of paper trees. They're also nicely collapsible so stick some in some Christmas cards! Or glue one onto a card to make one into a Christmas card:
You can make all sorts of sizes for your forest, but here are some templates for a starting place. For a larger 10" tree print up these two pages onto card stock.
Cut out, decorate and put together. It's easier to stand them up if you fold each half of the tree down the middle length-wise before fitting the slits together. And taping them on the resulting seams is not a bad idea either.
For a smaller 7" tree, print this up on card stock: