Store-bought hydroponic trays used in most ebb & flow systems can run several hundred dollar a piece, though they can be built for less than $20. If you are growing indoors and are not confident in your ability to build a leak-free hydroponic tray, do not attempt to build one, as water and electricity do not mix.

A hydroponic tray can be build with just 2x4s, plywood, plastic garbage bags, nails, glue, and caulk. The first step is to determine the dimensions you want for your hydroponic tray, a rule of thumb is to make your tray rectangular, to avoid excessive water weight in the middle of the support 2x4s.

Once you have your dimensions figured out, make a sturdy 2×4 frame. This frame will be the walls of your tray. Once your frame is complete, trim your plywood to fit the base of your frame. Densely nail the plywood to the bottom of the frame.

Now to add support, measure out 2x4s to go across the short dimension of your tray, nail them through the plywood into the frame. These supports should be spaced about every 18″.

The frame of your hydroponic tray is now complete, now to waterproof it. Put a thick caulk seal across every edge on the inside of your tray and let dry 1 hour.

Now take several trash bags and slice them down the side in order to produce plastic sheets. One at a time, add glue to the tray (or previous plastic layer) and line the tray with several layers of plastic, overlapping as much as possible.

There you have it, a basic hydroponic tray, depending on your setup, you may need to drill a hole in the bottom to attach a siphon, if this is the case, make sure you seal it well with caulk.