Measurements

• Measure the window frame and trim to determine the width of the wooden box. Keep it 8 to 10 inches high to provide room for roots of growing plants. Cut five cedar wooden boards for the window box based on your measurements.
  
  

Assembly

• Each box is composed of two same-size boards for the front and back, two same-size small boards for the sides and a board for the base. Glue the four edges of the base board and join the two long and two short boards to it to form a rectangular planter. Drill a row of wood screws along the lower end of the wooden box, spaced 4 inches apart, to secure the four walls to the base. Turn the box over and drill 1/2-inch-wide evenly-spaced drainage holes through the base.
  
  

Considerations

• Use 1-inch-thick, rot-treated wooden boards for outdoor window boxes that withstand natural elements and last many years. Using thicker boards increase the weight of the planter, making it harder to remove during the winter.