Start with a square sheet of paper
Fold the paper in half both ways
Unfold it after each fold
Fold each corner toward the center
Fold the top and bottom edges toward the center
Unfold the top and bottom folds
Fold the left and right edges toward the center
Unfold the left and right folds
Lift the top and bottom sides along the crease lines
Fold the side flaps inward to form the box walls
Press the corners firmly to shape the box
Repeat with a second sheet for the lid if needed