Create a Blintz Base
Crease and unfold the paper (Their should now be a fold line running down the center of the paper)
Crease and unfold. (their should now be two perpendicular lines that intersect in the middle of the paper)
Fold the Blitz base into a 4 by 4 grid.
Fold the Blitz base on the north/south axis. (your blintz base should now look like a vertical rectangle)
Crease and unfold. (there should now be a line running down the center of the blintz base.
Fold the blintz base on the east/west axis. (the paper should now look like a horizontal rectangle.
Crease and unfold. (the blitz base should now be divided into four quadrants.)
Unfold the blintz base into 4 vertical rectangles.
Finish the box
Feel along the southern triangle, locate the two right triangles on each side, pinch these together with the east and west walls. (The box should now have 3 walls, with two triangular flaps where the walls meet)
repeat the previous two steps on the northern triangle. (Your masu box should now be done! with four walls and four flaps securing them)