2. Draw and cut two support pieces from 8-inch pieces of 2-by-8.
3. Construct the shallow-pitched gable roof. You'll need two 17 1/2-inch-long pieces of 1-by-12, ripped to 8 inches, for the roof bottom, and 1-by-3s for the roof sides. The bottom pieces meet at the center peak with edges cut at 75°. The same angle repeats in the mitered side pieces, which should extend 1/8 inch past the bottom edges to create the drainage slots.
4. Center and attach supports along the long sides of the base. Center and attach the roof. Position the roof so the drain slots clear the base.