If you wish to use the AutoPot AquaValve to supply water to a flat tray, you will require the AutoPot AquaValve Cover to ensure the valve & floats work correctly.
You can place the AquaValve & Cover in any sized tray, but you must ensure the following:
The tray must be kept flat and level,
A small weight must be placed onto the top of the AquaValve to prevent it floating,
The pots must be 5ltrs or more, otherwise you could waterlog plant roots in smaller pots.
Once in place simply connect the AQUAvalve to a tank, using a length of 6mm pipe and a filter. Although a very basic method, this homemade system following the guidelines above can be very effective.