Cut four 35-inch 2-by-4 board pieces to form the legs of the butcher block island. Measure the boards with a tape measure and mark cut lines with a pencil and T-square. Lay the boards onto sawhorses and make cuts with a circular saw. Measure and cut four more 2-by-4 pieces to a length of 28 inches, and an additional four short pieces measuring six inches long.
Place one of the 35-inch boards across the sawhorses and place two beads of wood glue down the length of the large face. Squeeze lines of glue down the face of one 6-inch board as well. Lay the 6-inch board onto the larger board with the glue sides facing each other. Position the smaller board 1-inch higher than the end of the longer board to create a notched look. Position three 3-inch wood screws equidistantly on the 6-inch board and drive them into the longer piece using an electric drill. Repeat the construction of the other three legs exactly as the first and set all the legs aside.
Set a sheet of plywood on the sawhorses and measure a square 35 inches wide and 43 inches long. Draw cut lines with a straightedge and pencil, then cut the piece for the island's shelf with a circular saw.
Place a line of wood glue over the top of the notch in each of the legs. Fit the cut plywood shelf onto the notch of all four legs. Ensure a straight alignment using a construction square and drive two 2-inch wood screws through the plywood into the legs to secure them.
Measure and cut a 2-by-6-by-8 board into a 43-inch piece and a 31-inch piece with a circular saw. Repeat this to make a total of four boards.
Lay a long side of the island frame flat on the ground and place one of the 43-inch 2-by-6 boards on the inside of the boards lying on the ground. Position the top of the board so it is one inch below the top of the legs and drive three 3-inch wood screws into the board and each leg. Turn the frame over and repeat this for the other long side.
Attach two equally positioned angle brackets to the wide face of one of the 31-inch boards. Get the brackets positioned right at the end of the board and mount them with a 1-inch wood screw. Place two more brackets on the other end of the board and then repeat the process for the second 31-inch board. Lay the frame on the ground with the short side down and align the 31-inch board with the top of the long 2-by-6 boards. Place 2-inch wood screws through the brackets and into the long boards to complete the top frame.
Measure and mark three 35-inch boards on one 1-by-3-by-10 board and draw cut lines. Lay the boards out across the frame from one long 2-by-6 to the other. Space them equally across the top of the island and drive two 1-inch wood screws down through the face of the 1-by-3 boards into the top of the 2-by-6 channels.
Set the 40-by-46 piece of butchers block on top of the island and center it exactly in the space. From underneath, drive 1 1/2-inch finishing screws up through the 1-by-3 boards and into the butcher block. Have an assistant hold the block down while driving the screws to keep it from lifting. Place at least 4 screws into the butcher block to secure it.