It's pretty structural as far as paper cubes go and can hold a fair amount of stuff (which would make it ideal as a small gift box).
Step 1: Go get stuff.
A cutting board
An 11" x 17" piece of paper (or equivalent)
An Exacto knife
Step 3: Draw some lines.
The fold lines should be 1 3/4" in from each border. This will leave a 2 1/2" square in the center.
Step 4: Fold.
Once done, you are going to want to fold the paper back in the opposite direction so that when you actually make the cube, the pencil lines will be on the inside.
At the end of both sets of folding, go back and erase the pencil lines as best you can.
Step 5: Fold in corners.
Step 6: Start the box.
Do this for every corner until you have half a cube.