Use hot glue on the seams - I tried a gluestick first, but what was I thinking - hot glue did the trick. Cut a rectangle and glue the 2 short ends together. You'll have a tube. Then glue one end, like shown:
For extra spunk, I ran both ends in my paper-crimper-thing - - it takes a little muscle since you're crimping on top of dried hot glue, but it's doable.