Open up the flattened packing box and fold it into its rectangular shape.
Fold the flaps on the bottom of the box shut. Fold the shorter flaps first, then fold the longer flaps over them. Continue holding the flaps shut with your hand.
Tape the seam running along the bottom of the box where the two folded end flaps meet. Start the tape on the side-end of the box, near the middle, centered with the seam on the bottom. Roll the tape along the side of the box, over the closed center seam on the bottom, then down onto the opposite side-end, stopping near its middle.
Push down lightly on the center of the taped seam to compress it. Apply tape to the two open seams on the ends of the box's bottom. Center the tape over each seam and cover from corner-to-corner on the box.
Flip the box over. Fill it normally, then close the top of the box and repeat the taping procedure to finish sealing it shut.
