This kerfed box has only two seams, one between the bottom and the side walls, and one to seal the side walls. Rather than cut the sides to their finished dimension a plank of cedar is heated and bent to create a watertight box.
Three notches are cut in a cedar plank. The notches stop just short of cutting the plank into sections. The red lines in the drawing below indicate the fold lines for a kerfed box. Pits are dug in the ground and rocks are heated until they are red hot; then water is poured in the holes and the plank is placed over the steaming hole and covered to conserve heat and steam. When the plank has steamed sufficiently to soften the wood fibers, it is slowly bent to a ninety-degree angle. The one side seam is pegged together. Then a plank is cut to the dimensions of the box and pegged to the bottom. The result is water-tight construction.