Start with a square sheet of paper
Fold the paper in half horizontally, then unfold
Fold the paper in half vertically, then unfold
Fold each corner to the center crease intersection
Fold the top and bottom edges to the center line
Unfold the top and bottom edge folds
Fold the left and right edges to the center line
Unfold the left and right edge folds
Fold the paper along the existing creases to form the box walls
Lift the side panels upward
Tuck the corner flaps inside to lock the shape
Press the base flat
Repeat with a second square sheet to make a matching lid if needed