Place the 1-by-24-by-36-inch boards with the 1-by-36-inch edges flat on a work surface so that they are parallel to each other and 18 inches apart. These are the front and back sides of the chest.
Insert the 1-by-18-by-24-inch boards between the ends of the front and back sides to form a rectangle. The 1-by-18-inch sides edges should be flat on the work surface. These are the ends.
Drive flush trim wood screws every 3 to 6 inches through the front and back sides into the edges of the ends along the joints with a screw gun.
Align a 1-by-20-by-36-inch over the top edges of the rectangular assembly. This is the bottom of the chest. Drive flush trim screws every 3 to 6 inches around the edges of the bottom into the front and back sides and ends of the assembly.
Turn the assembly over so that the bottom is flat on a work surface. Align the remaining 1-by-20-by-36-inch board over the assembly so the edges are flush. This is the lid.
Hold the lid in the open position and center the piano hinge at the joint between the back edge of the lid and inside back side of the storage chest. Drive the provided screws through the holes in the hinge into the back edge of the lid and inside back side of the storage chest with a screw gun.
Adhere a felt pad to the front corners on the underside of the lid.
Fill the screw holes with wood putty using the blade of a putty knife. Allow the putty to dry and sand it flush with the surface of the wood with fine-grit sandpaper.
Apply a clear finish to the outside of the storage chest. Leave the inside natural to allow the natural fragrance of the cedar to deter moths and other nuisance bugs.