Scissors (or another way to cut the cardboard)
Glue (I think regular glue is better than a glue stick for this because you can move the pieces a little still)
A way to hang it, like a picture frame hanging kit.
Directions are so simple!
Have a piece of cardboard to glue the smaller pieces onto.
Cut the corrugated cardboard into different sized squares and rectangles.
Experiment. There IS no wrong. If something doesn't look right, you can cover it up with more pieces of cardboard.
Hint: Only one side of the cardboard will show the "ridges." Have that side face out.
Ideas: This might be neat if the pieces were painted with a metallic spray paint. Or different colors. If you're doing it as a family project and aren't against painting, you could take a family vote. (See if they gang up against you! *g*)