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 last two folds
Fold the left and right edges to the center line
Unfold the last two folds
Fold the top and bottom edges again to the center line
Open the side flaps along the crease lines
Lift the side walls upward
Press the corners inward to form the box shape
Fold the remaining flaps over to lock the sides
Repeat with a second sheet to make a matching lid if needed