Bevel the top of all four 1x2 legs with a miter saw. Make a mark, 1/4-inch in, at the top of each leg. Make another mark 1.5 inches down from the top at the edge. Draw a line between the two marks and make the bevel cut along that line.
Make a 1/2-inch mortise or indent cut on both sides of each end of the 2x2 top brace -- one mortise for each leg -- starting 2 inches in from the brace ends. Each cut should be the exact width of the legs. Attach the beveled top of each leg inside a mortise with wood glue and screws.
Attach two 60-inch shelf supports on each side of the frame with wood glue and screws. Place the bottom edge of the lower shelf support 24 inches up from the leg bottom. Locate the top edge of the top shelf 24 inches down from the top. Attach the cross-braces to the legs the same way, below the lower shelf.
Cut the 16-inch 2x2 into eight 2-inch pieces. Glue then screw these small blocks near the corners of both shelves so the blocks fit just inside the shelf support. This will keep the removable shelves from sliding off. Coat the shelves with polyurethane.
Fasten a shop light to the top brace. Attach an eye-bolt to the hood top at each end with the eye face-up. Screw two eye-hooks into the bottom of the top brace, the same distance apart as the hood’s eye-bolts. Attach an S-hook and a 2-foot length of chain to each eye-hook. Hook the chain onto the eye-bolts to hang the light.
Connect the two lower shop lights with the 18-inch cross-members. Place the two light hoods upside down so that they are parallel with the cross-members that run between them near each end. About 2 inches from the ends of the 2x2s, attach screws through the top of each hood from the underside.
Turn over the attached light hoods. Screw two eye-bolts into each of the 2x2s on top, 1 inch from the ends. Attach the cross-members to the top shelf supports, from below, just as you attached the top light to the top brace.
Slide the top shelf and the bottom shelf into place. Insert the light bulbs. Plug each hood into a power strip. Turn the power strip on when you’re ready to start your first seeds.