Take the cabinet doors off the cabinet by removing the screws in the hinge using a power drill. Set the doors aside.
Cut out the bottom section of the cabinet using a circular saw. Cut as close to the edges as possible.
Remove the edge sections using a hammer and a chisel. Place the chisel at the joint and lightly tap the end of the chisel with a hammer. This will break the glue joint and allow you to remove the entire cabinet bottom. If staples are present, break them off using pliers.
Measure the cabinet bottom using a tape measure.
Cut the cabinet bottom out of new material using a circular saw. Cut slowly to avoid jagged edges.
Place a small amount of carpenters glue around the joints. Place the cabinet bottom into position.
Nail the bottom to the cabinet sides. Place the nail on an angle through the bottom and into the sides. Tap the nail into position using a hammer. Place the finish nails about 6 inches apart.
Fasten the doors back onto the cabinet using a power drill.