First you need to take apart the box and use just one section for the perfect size for the quarter pipe. You need to completely cover it in duct tape for smoothness. For now, set that section to the side. Take another section and cut it to the angle you want your quarter pipe to be at(the picture is a good example), you will need to make two exactly the same. You can cover the angle thing with duct tape(I did) but it is only for looks. Then take the piece you set aside and curve it onto the angle thingy. As you hold it on, tape them together very tightly.
Step 3: That's It
If you want it to be more stable, tape it to the ground. If you have any suggestions please leave a comment. Please vote for me!!!