Cut eight 18-inch pieces of 2-by-4-inch lumber.
Assemble four 18-inch pieces into a rectangle by laying the pieces on their narrow edges and inserting two screws through each corner. Repeat to create a second rectangle. These rectangles will be the feet of your bench.
Cut three 8-foot-long 2-by-4-inch boards in half. Stand the two rectangles you made earlier on their short ends, parallel to each other, 3 feet apart. Position five of the 4-foot-long 2-by-4-inch boards on top of the two rectangles. Spread the boards out evenly so they extend slightly over each side.
Drill a 1/4-inch hole through the 2-by-4-inch boards into the tops of the rectangular legs on each end of the booth bench seat.
Drop a 4-inch carriage bolt into each hole. Strike the top of the bolt with a hammer to set the bolt in place. Slip a washer over the end of the bolt and tighten a nut over the carriage bolt using the wrench.
Sand any rough parts of the bench with 200-grit sandpaper.