Line up two long boards parallel. Set them 12 inches apart. Make the ends flush. Place the wide face of a brick on each side of each board to hold it in place.
Insert a 12-inch board between the longer boards spanning the width between the boards. The ends of the short board will touch the sides of the longer boards. Line up the short board so 2 inches of the long boards extend beyond it. Repeat this step with another 12-inch board on the opposite end of the 54-inch boards.
Drill three screws equidistant through the sides of the long boards into the ends of the long boards. This is one of two frames for the bench.
Construct the second frame using the same method to build the first frame. You should have two identical frames with the end boards 2 inches in from either end of the side boards.
Set a post leg at each right-hand corner formed by the frame. One pair will be inside the frame while the other pair is outside the frame. Drill two screws through the short boards into the post at opposite corners. Drill two screws through the long boards into the post centered at the top and bottom.
Line up the second frame with a short side against the posts. The extended end of the long boards should butt against each other along the outside face of the posts. Drill two screws through the short boards into the post at opposite corners. Drill two screws through the long boards into the post centered at the top and bottom.
Set a post leg at each of the two remaining inside corners. Drill two screws through the short boards into the post at opposite corners. Drill two screws through the long boards into the post centered at the top and bottom. You will have six legs for the bench.
Flip the entire frame upright to stand on the legs.
Line up the four 60-inch boards side-by-side. Make the ends flush. Measure and mark 3 inches along the two outside boards. Hook the tape along the side of one outside board at the mark. Pull the tape across to the opposite mark. Draw a line across the boards using the tape as a guide. Repeat this step on the opposite end of the boards.
Lay two of the 60-inch boards lengthwise at one end of the frame. Line up the markings you made with the end of the frame. This provides a 3-inch overhang at the side of the bench. Make the long ends flush with the frame. Hammer three nails through the ends of each board to the frame. Hammer five nails equidistant through each board to the frame along the exterior sides.
Sand down the rough spots and corners with medium-grade sandpaper. Use fine-grade sandpaper over the entire bench to finish it. Brush off the bench with tack cloth.
Stain the surface with wood stain using the paintbrush. Allow the coat to dry. Apply a second coat.