Measure the door frame's height and width. Subtract 1/4 inch from the measurements to allow for a 1/8-inch clearance on all sides of the screen door.
Mark the door measurements on the sheet of plywood. Using a table or circular saw, cut out the door.
Measure 8 inches from the top and sides of the door and mark it on the door. Also, mark 12 inches from the bottom edge of the door to allow for a kick plate. Indicate the handle on the door, at 33 inches from the door's bottom edge. Centering on the door handle, mark a pair of horizontal lines, 8 inches apart.
Draw your custom design on tracing paper. For example, use the outline of a dog, a cat, a bird or a stencil for your house numbers. The bottom edge should be a straight line since your design must meet a solid area of the door.
Lay the transfer paper on top of the screen door. Carefully align the tracing paper over the transfer paper. Overlay the bottom edge of your design onto the top edge of the two parallel lines in the middle of the door. Trace the design with a sharp pencil to transfer it onto the door.
Drill a small starter hole in the corner of the pattern. Using your jigsaw, slowly cut out your design on the screen door frame.
Sand the screen door with 180-grit sandpaper until smooth. Wipe the entire surface of the door with a tack cloth to remove the wood dust.
Prime the plywood with an exterior grade latex primer. Apply two coats of primer with a paintbrush. Then apply two coats of paint on both sides of the door, using a high-quality, exterior-grade, gloss latex paint. Allow the primer and paint to dry between coats according to the manufacturer's directions.
Place the door on a flat surface, with the outer surface down. Roll the fiberglass window screen over the cutout areas. Staple the screen to the plywood every 2 inches, all the way around the cutout areas. Trim the excess window screening with scissors, except behind the decorative cutouts.
Measure and cut decorative molding to fit around the outer edges of the screened area. Trim the corners of the molding with a miter box and saw.
Run a bead of construction glue along the back of the molding and press into place. Predrill through the molding and into the plywood before tapping 1/2-inch finishing nails into the wood. Turn the door over and add decorative molding around the screened openings to make a finished edge.
Turn the door over and install a kick plate if desired. Install the kick plate 1 inch from the bottom of the door and centered from side to side. Predrill the screw holes and screw the plate to the inside of the door.
Add a screen door handle, hinges and a pneumatic screen door closer according to the package directions.