Loosen the screws or bolts to remove the cabinet door from the hinges, paying attention to keep a firm grasp on the door to prevent it from slipping or falling out of your hands.
Set the cabinet door with the bowed side up on a piece of plastic tarp or newspaper on a flat outdoor surface, such as your lawn or walkway.
Dampen a white cloth with plain water and lay it onto the bowed section. Set a weighted object, such as a pile of books or brick, on the white towel.
Allow the cabinet door to remain weighed down and under the sun’s rays for one to two hours before removing the brick and damp cloth. If the plywood is still bowed, rewet the cloth and weight the cabinet door for one to two hour increments until its surface is flat.
Hang the cabinet door in its original position.