Well, to make a Christmas tree out of cardboard, you will need the following materials: cardboard, scissors, tape, glue, and some decorations. First, cut out a triangle-shaped piece of cardboard to use as the base of the tree. Then, cut out a series of smaller triangles to create the branches. Attach the branches to the base using tape or glue. Once the structure is complete, you can decorate it with ornaments, lights, and garland. Voila! You have a beautiful cardboard Christmas tree.