Over time, the repeated moisture absorption and drying of a cutting board can cause it to warp. It is difficult, as well as unsafe, to cut food on an unstable cutting board. Fortunately, wood can be very forgiving. Before throwing away your cutting board and buying a new one, try soaking and clamping it to remove the bow. Regular refinishing of your cutting board will help to keep it from warping again.
Submerge and soak the cutting board in a bucket or tub of hot water for at least 1 hour.
Place your board on a worktable with the convex side of the warp facing down. Insert a small dowel or a thin, square or round stick of wood under the warp. The stick should be no thicker than 1/2-inch and should run the entire length of the warp. Clamp the cutting board so it bends the other direction, over the stick. Clamp for at least 12 hours.
Flip your board over and clamp it for another 12 hours.
Treat your board by rubbing it down with mineral oil. This will provide a natural finish that will keep the board from absorbing too much water and warping again.
Refinish you board periodically with mineral oil.
Refrain from ever letting your board soak or stand in water. This will cause it to warp again. Wash your board with a soapy sponge, rinse and immediately hand dry. Use both sides of your cutting board. Only using one side of your cutting board will cause a lot of moisture to soak into one side of the board, but not the other. This can also cause your cutting board to warp.