Align the 2-inch edge of one of the 3-foot-long boards with the face of another to start building the structure of the bench. The two lumber sheets should form a right angle. Make sure the edges of the board are flush.
Attach the two boards with 4-inch nails. Hammer in one nail every 2 to 4 inches along the joint of the two pieces.
Place a 3-foot board on the face of the structure to form a right-angled U-shape. One board should have the 2-inch edge of two sheets of lumber on it to keep the bench even.
Attach the two boards with 4-inch nails. Hammer in one nail every 2 to 4 inches along the edge of the two boards. Leave the fourth 3-foot board aside, as it will be the top of the storage bench.
Place one of the 2-foot-by-2-foot boards at the open end of the U-shape to give the bench a closed side. Attach the board to the 2-inch edges of the bench structure with 4-inch nails.
Repeat Step 5 with the other 2-foot-by-2-foot board to close off the other side of the storage bench.
Attach two hinges to one 2-inch edge of the 3-foot portion of the storage bench. Place the hinges a foot apart so the bench will open and close smoothly. Attach the hinges to the bench with 2-inch screws.
Attach the remaining 3-foot-long piece of lumber to the hinges to finish the bench. Attach the board to the hinges with 2-inch screws.
Use a paintbrush to cover the bench with weather-resistant stain so it will withstand rain and snow. Allow the bench to dry before using it.