Arrow Storage Products ED108 Owner's Manual & Assembly Instructions page 14

4. Construct a wood frame using four planks of 1x4 (19 mm x 89
mm) lumber.
5. Pour in concrete to fill in the hole and the frame
giving a total of 4" (10,2 cm) thick concrete. Be sure
surface is level.
Allow 3 - 5 hours for construction and a week for concrete curing
time.
Note: Finished Slab dimensions, with lumber removed.
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