Drill a hole that is at least an inch and a half in diameter in the center of one of the 8-inch-long cedar sheets. This will provide a place for the birds to enter and exit the birdhouse.
Align the 2-inch edge of the board with the hole in it with the 8-inch face of one of the other boards. Ensure that the edges of the boards are flush. Attach the two boards with 4-inch nails. Hammer in one nail every 2 inches.
Align the other 2-inch edge of the board with the hole with the 8-inch face of a third board to create a U-shape. This will be the front and sides of the birdhouse. Attach the boards with 4-inch nails. Hammer in one nail through the face of the front board until the nails are flush with the wood.
Place the remaining 8-inch-long board on the open portion of the birdhouse to close off the U-shape. Align the face of the 8-inch board with the 2-inch edges of the side boards and attach them with nails. Hammer 4-inch nails through the face of the back board until the heads of the nails are flush with the wood.
Place one of the 6-inch-long boards on top of the birdhouse to give it a roof. Attach the board with 4-inch nails. Hammer in one nail every 2 inches along all four sides.
Repeat Step 5 with the remaining 6-inch-long board to complete the birdhouse.