The shelves will be hidden inside the planters, so use a lower-grade redwood. Set a bottom frame on top of four 2x4s placed side by side, and trace the outer shape of the frame onto the planks. Cut out the curves with a jigsaw. Use wood glue and biscuit joints to hold the planks together. Screw two 2" x 2" braces to the underside of the shelf. Drill six holes through the shelf for drainage (figure E). Make another shelf for the other planter. Attach each bottom frame to 1" x 6" redwood planks cut to 16 inches long, using galvanized screws. Also attach the top frames. Set the shelves at the desired height (about 9 inches down from the top frame). Drill screws through the back of the planters into the shelves to hold them in place (figure F).
To enclose the planter frame and shelf, use top-grade, all-heart, kiln-dried 1" x 3" redwood slats, which will last forever (available for $1 per foot). Screw the slats to the outside of each planter. Cut and build redwood caps in the same way that you made the frames and screw them to the top of the planters. Finish the edges of the caps using a router. Figure G shows the completed planters.
Step Three: Constructing the Bench
For this two- by four-foot bench, set up a simple rectangular frame using 2" x 6" redwood planks, with supporting planks in the middle spaced 16 inches apart. Drill 3-inch screws to attach all the planks. For the seat, place 1" x 3" redwood slats on top of the frame, using an 8-penny mail as a spacer between slats. Using screws, fasten the slats to the frame. Round out the edges of the bench seat with a router for a finished look.
Prepare the bench site by removing any low-hanging branches and rake the surface level. Stake a 2x4 into the ground to contain the pebble base. Rake out a couple of inches of landscaping pebbles for a comfortable, stable base. Add a light layer of cedar bark mulch around the base and surrounding area.