20mm shutterply (or similar sturdy board)
2 x 600mm x 620mm (ends)
2 x 900mm x 620mm (sides)
1 x 940mm x 620mm (base)
The sides and ends are fastened on to the top of the base, not the sides of the base.
The sides are attached first to the base, positioned 20mm in from the corners (ie centred along the length of the base).
The ends are attached to the base and sides, flush to the edges of the sides.
Add square brackets to the bottom all around and to the sides for added strength.
Drill four 8mm holes horizontally in each end and tie in lengths of sturdy rope for loops on the outside to act as handles for the box.
Cut two small slots in the top of either end to act as guides for the baling twine, and on one side just below each slot partially screw in a screw to act as a hook for the twine.
To see the box in use, watch the video below: