Choose untreated wood or exterior-grade plywood
Cut a back panel, front panel, and side panels
Make the box tall and narrow
Roughen the inside surfaces for grip
Add ventilation gaps near the top
Seal all exterior seams with caulk
Assemble the box with screws
Leave the bottom open or add a landing area
Paint the outside with dark, non-toxic exterior paint
Mount the box at least 10 to 15 feet high
Place it in a sunny location
Face the box south or southeast
Keep it away from bright lights and obstacles
Secure it tightly to a pole, building, or tree
Inspect it periodically for damage
Avoid using preservatives or pressure-treated wood