Place eight planks of wood side-by-side on a flat surface. Press the boards close together so there is not a gap between them. Have all of the wood pieces precut at your local home improvement center.
Set one 48-inch piece of wood horizontally across one end of the planks. Set another 48-inch piece horizontally along the other end of the planks. Place the last 48-inch board horizontally in the center of the boards, 33 inches from the top end of the planks.
Drill six wood screws though the horizontal planks at the top and bottom ends and into the middle horizontal piece across the eight wood planks. Place three on the top edge of each horizontal board about 1 inch from the edge and three screws along the bottom edge of each horizontal board about 1 inch from the edge.
Turn the door over and press wood putty into the holes made by the wood screws. Leave the flat metal tops of the screws visible on the other side, or front, of the door.
Sand both sides of the new door with medium 80-grit sandpaper. Wipe the sanding dust away with a tack cloth.
Add a coat of the oil-based wood primer to one side of the door. Use a paintbrush to apply the thick primer. Wait four to six hours for the primer to dry. Turn the board over and add a coat to the other side of the door. Let the primer dry for four to six hours.
Paint the door with a water-based latex paint. Use a small sponge roller and paintbrushes along the edges of the boards.