Cut 18 pieces of 1-inch-by-2-inch lumber into lengths 18 inches long. Some lumberyards will do this for you if you do not have a table saw of your own.
Lay the 18 pieces with the 1-inch sides up in a square on your workbench.
Begin gluing one 1-inch-by-2-inch piece to the piece next to it. Use only glue that is FDA approved "food safe." This distinction can be found on the label of the glue bottle.
Clamp the glued wood in three evenly spaced sections and allow the glue to dry overnight. Spacing the clamps 5 inches apart will ensure the glue will spread and adhere properly.
Sand the glued cutting board by loading the hand sander with 100-grit sandpaper. Sand both the upper and lower surfaces, as well as the sides of the board.
Wipe excess sawdust from the board with a clean cloth dipped in mineral spirits. Repeat the process using 200-grit sandpaper and then again with 400-grit sandpaper for a smooth surface.
Season the butcher-block cutting board by applying multiple layers of mineral, walnut or tung oil to the surface of the board. Allow each layer to soak into the wood before applying the next layer. When the wood will no longer soak in the oil, the cutting board is ready to use.