Less expensive substitutes for Earthboxes© can be made from Rubbermaid© containers. The platform is either made from the lid of the tote, or from a second tote placed inside the first. The platform must have holes for aeration and larger cutouts for soil to be in contact with the water and act as a wick.
As seen in the first photograph, the platform can have sections of PVC with drilled holes for circulation to hold the platform above the water. (shown upside down)
The second photograph shows the completed, self-watering container. A black plastic trash bag can be used as a mulch cover. Find Instructions.