In the attachment, superthick green is what becomes the bottom of the box; thin green is what becomes the top of the box. Black marks the outline, red marks all internal cuts; shades of gray (possibly hidden by red or green) mark folds.
- Begin with a square piece of paper (thin black outline). Until you're used to it, it's best to use at least 5 inches by 5 inches.
- Fold and unfold the two diagonals (thin dark gray) so you get the center.
- Fold opposite corners to the center (thick dark gray; this will become the top edge of the box), then fold them again into the center (thick light gray, which by this time is also the thin light gray). Unfold, then repeat with the other pair of corners.
- Cut out the middle triangles for each side (thin red) and cut in the flaps (thick red).
- Refold the corners with flaps to the center, then bend them into 3D. Finally, fold the corners without flaps over the flaps to lock it.
- The result is a box that holds its shape, even if you were sloppy in making it. There are two layers of paper at every point (except 3 where the flaps are).
When doing perspective, it's probably best if the box is distant from you. And, you'll want to make sure that all the corners are square. So, you should probably not be sloppy on the one you actually use.
If I'd thought of showing you this via hangout, I probably would have used the 451 joke ...
