Divide a rectangular sheet of paper into four equal parts (drawing a). Then fold the ends of the longer sides like this, to meet in the middle (drawing b). Fold the four corners to the dotted lines (drawing c). Fold the edges of the paper that meet in the middle (drawing d) in the direction of the arrows marked in figure c. Grab the short sides of the paper and bend them like this, to form a box (drawing e).

Folding box.