A step by step guide to make your own treasure chest is available here.
Using pallets can be a resourceful way to obtain wood, as your local DIY or gardening shop may give them away for free. Australian maker Pat, aka Crow Builds, also had an old styrofoam box to hand and decided to upcycle them into a treasure chest cooler.
The lid of the chest is half a tetradecagon (14 sided shape) with each of the wooden slats cut at an angle. Even the padlock has been made from an offcut of wood. Pat suggestions, "If you want to add a cool effect, put some battery powered fairy lights in the bottom before putting in your ice."