Using 2x4 lumber construct a 4x4 foot frame. elevate frame using hollow tile to the desired height.
Cut a 3/4 inch plywood to fit the 4x4 foot frame. Secure to the bottom of the 4x4 foot frame.
Cut expanded polystyrene foam board to fit 4x4 foot frame. Using a 2inch hole saw drill holes 8 inches apart starting 4 inches from any corner.
Remove foam board. Using 4 mil black plastic liner, cut plastic so that there is 8 inches hanging over each side. Begin filling plastic with water.
While the tank is filling, ensure that the frame is level. If unleveled use shims to level the tank. Also, press plastic liner in the corners of the tank. Mix in fertilizer based on labeled rates.
After tank has filled to 1 inch from the top of the tank, begin securing the plastic to the outside of the tank using a staple gun.
Place 2 inch net pots in each hole on the foam board. Suspend foam board over tank. Ensure that there is at least 1/4 inch of water at the bottom of each net pot.
Plant seedlings in each net pot and allow to grow. No refilling of water and nutrients are needed till the next crop.