I needed a large esky for Christmas day but couldn't afford one so bought a 80 litre storage tub from Bunnings, filled it with ice and it worked well. I decided to build a timber box and frame around it with a lid and packed the sides with polystyrene foam. I painted the box to match my outdoor furniture and I am very happy with the results. Stays cold and lasts as long as any cooler. I already had timber offcuts and leftover paint so it was a simple and affordable project.
How to build an ice box
Cut eight pieces of 90 x 18mm Pine to 800mm lengths for the legs. Glue and screw two pieces together at right angles for each leg.
Use 7mm plywood to build around the four sides of the storage box, leaving about 25mm for wriggle room. Place the four sides together around the storage box on the floor to make sure there will be enough room between the timber and the plastic to stuff styrene foam (cut from foam boxes) around the sides to insulate.
Lay two of the legs on the floor and put a long piece of ply inside the angles, and then glue and nail. Do the same for the other side.
Put a frame around the top edge and another frame inside to fit into the 7mm ply lid. Add a hinge at the back of the lid.
Turn it upside down with the storage box inside and slide pieces of styrene around the sides and bottom to insulate. Put a base on it and turn it up the right way.
Drill a hole through the bottom big enough for a cork to drain melted ice.
Put another piece of styrene inside the lid and make sure it all works, and then sand and paint.
Attach a chain or cord inside the lid to stop the lid opening all the way.