Measure height and width of windows. Decide how long and how many boards wide you want to make your shutters.
Cut your boards to the appropriate length.
Decide on spacing between boards. If spacing is desired, use evenly sized spacers such as coins, then clamp boards together. If you do not want space in between boards, clamp boards together, making sure the ends are even with each other. *Without clamps - have one person hold boards tightly while other assembles.
Measure the final width of your shutters, including any spaces. Cut supports pieces to the appropriate length, at least two supports per shutter.
Attach support pieces horizontally across boards about 6" from the top and bottom. First attach with wood glue and small finishing nails from the front. Then carefully turn shutters over and screw into support pieces from behind. For best results, predrill holes to prevent wood from splitting.
Stain or seal shutters, if desired. Let dry completely before handling.
Attach shutters to the house using exterior screws, one in each corner. Use a shim or thin board behind the shutter to preserve a small space between the shutter and siding. Make sure the screws go through both the shutter and the shims.