Getting the Pieces Ready
Start by cutting four of the 2x4s in half, so that each piece is 48 inches (1.2 meters) in length. Cut an additional 2x4 in half and take 8 inches (20 centimeters) off of just one of those pieces so that you have another 48-inch slat and one 40-inch (1-meter) board.
On another 2x4, mark off 40 inches and use that piece to cut two trapezoids, each 20 inches (50 centimeters) in length at the base and with 15-degree angles on each side. Use the rest of this 2x4 to cut three parallelograms that are 17 inches (42 centimeters) in length and also feature 15-degree angles.
Cut your seventh 2x4 into four pieces. The first is a 31-inch (79-centimeter) long slat with a 90-degree angle on the left side and a 15-degree angle on the right side. Make the next two pieces trapezoids that are 23.75 inches (60 centimeters) at the base and have 15-degree angles. The last piece should be a 17-inch long parallelogram, also with 15-degree angles. Finally, saw the last 2x4 into another 31-inch long board with a 90-degree angle on one side and a 15-degree angle on the other.
Now you're ready to start putting the bench together.