It's a great project for weekend DIYers on a budget: With a few woodworking power tools and modest skills, you can achieve beautiful results.
Cutting rabbets and slots
The corner posts (A) are the most complex pieces to cut. First cut the four parts to length; then cut the 1-1/2- x 1-1/2-in. rabbet along one corner of each. You can do bore out most of the rabbet with a drill and then clean it out with a chisel, but I used a router and a 3/4-in.-dia. straight bit with a 1-1/2-in. cutting edge (photo, below left) because it left much less wood to chisel out at the end of the cut. I made four passes for each rabbet, moving the router fence 3/4 in. or raising the bit 3/4 in. after each pass. After the final pass, I squared the corners of the rabbet with a chisel (photo, below right)
Next, I marked and cut the 3-1/2- x 1-1/2-in. slots for the bottom cross braces. Note that there are two right legs and two left legs, so be sure to make the slots on opposite sides — you can't just cut them all the same and assume that you can rotate them. (Don't ask how I learned that.)
Cutting the parts
Once the corner posts are done, the rest of the cutting is pretty straightforward. All you need are a miter saw and a table saw, or a circular saw with a cutting guide. I cut the bottom cross braces (B), middle cross braces (C), cross-brace supports (D), shelf slats (E), and post caps (H) with a miter saw to the lengths indicated in the plans. I cut the 1x12 side panels (F) and end panels (G) using the miter gauge on my table saw.
It was a bit tricky to cut the side panels (F) on my contractor's table saw, but using my roller stand as a table extension allowed me to slide the panels smoothly and perfectly straight through the blade. You could also use a circular saw with an auxiliary fence or an edge guide to safely rip the longer edges.
Assembling the planter
Assembly begins with the middle cross braces (C) and supports (D). I drilled pocket holes in all of the supports and then laid out the frame on my workbench, using five pipe clamps to hold it square while I drove pocket screws. Here you may see the limitations of using dimensional lumber: Both middle cross braces had a slight bow to them, but neither was unusable. I simply set each cross-brace support flush at both ends against the middle cross braces. A little tweaking with a mallet brought each support into position before I clamped it in place.
Once the frame was finished, I set up the four corner posts and, with the help of a friend, positioned the frame's corners in the posts' rabbets. I fastened the frame to the posts from the inside (photo, below left). Then I installed the bottom cross braces (B) in the same manner, making sure that everything was tight and flush before fastening the parts to create a nicely fitted, square frame with legs (photo, below right).
Next, I lowered the side panels (F) into place and drove 2-1/4-in. screws from the inside through the corner posts. With some gentle persuasion from a rubber mallet, the end panels (G) went in place; I also fastened them with 2-1/4-in. finishing screws.
To lay out the shelf slats (E), I used a 1-in. spacer and drove two 2-1/4-in. finishing screws through the ends of each slat. For the post caps, I used a more decorative type of fastener: No. 12 x 2-in. brass screws, for which I drilled countersunk pilot holes. To avoid drilling into the posts' rabbets, I drove the screws 1 in. from the ends of the post caps and centered at 1-3/4 in. With a 1/4-in. overhang on each end of the post cap, the pilot hole was in the middle of the solid wood surrounding the rabbet.
Finishing the planter
I was amazed at how solid yet lightweight the assembled table turned out. Cedar is a soft wood that doesn't weigh a lot, but the design and construction yielded a very sturdy piece of furniture that's easy to move. Before applying finish, I sanded all surfaces with 80-grit sandpaper, rounding over the edges to prevent splinters. I then applied a generous coating of teak oil (1 quart) to help preserve the warm cedar color.
Before adding plants, you could put a wood panel in the box and fill it with planting soil. I opted for the easier, cleaner method of inserting plastic tubs into the table. In either case, be sure to drill a few holes for drainage.
Now I'm ready to plant my tomatoes. At the end of the season, I'll just pull them out, spread the dirt over my lawn and rinse out the tubs for next spring.