Dig out at least 250 mm of existing soil to obtain a depth of at least 350 mm. The outer surface of the sandbox is 1,600×1,600mm and the height is approximately 100mm above ground. The construction and the work are the same as for the planting box. The coverboard provides rounded edges and serves as a backing board. It may be useful to screw a 34 x 70mm lip onto the outer edge of the backing board that protrudes above the board and holds the sand.