Making yarn Christmas trees is a fun and easy project that you can do with just a few supplies. Here's what you'll need: some green yarn, a piece of cardboard, scissors, and a hot glue gun. First, cut a piece of cardboard that's the size you want your tree to be. Then, wrap the green yarn around the cardboard until it's completely covered. Once you've got enough yarn wrapped around, use the hot glue gun to secure the end of the yarn to the cardboard. Finally, cut off any excess yarn and voila! You've got yourself a cute little yarn Christmas tree.