Here you go:
This one is cute
I have seen people use a post and bottom support pieces to hold the post up. Then they cut pieces of wood and attached them to the post. You could draw the tree shape on a pallet (at center board) and cut the wood with a jig saw. The wood that is cut off can be added as needed.
Laura, there are several ways and ideas. I have chosen one for you, but if you go into "explore projects" then "build" then type "build pallet Christmas tree" in the search box you will find many more.