The top of each leg is notched to provide extra support for the aprons. In turn, the aprons are secured to the seat with L-brackets. For added strength, four screws are then driven through the top of the seat into each leg and one screw into the centre of each apron.
Lay the legs on their edges and nestle one of the aprons into the uppermost shoulder cutouts. Position the legs 4" in from the ends of the aprons, square them up, then lock them in position with two #10 x 1½" plated screws per joint. (Driving the screws into pre-drilled countersunk holes in the aprons greatly reduces the chance of splitting, especially with wood that contains knots or wavy grain near the screw locations.)
Turn the seat upside down on your workbench, then centre the leg frame on top. There should be 2" of overhang on each end. I used pocket screws to secure the top to the aprons, though metal L-brackets work, too (as above). Flip the bench over and drive four 1½" screws down through the top into each of the legs, and one in the centre of each apron for added strength.
To create a weathered finish, I began with a coat of exterior latex paint in matte black. Once dry, a second coat was added (this time in dark green). Distressing was done with a ring of keys banged against the bench to create dents and dings, with a palm sander providing the necessary wear in all the places you'd expect. The idea is to remove some of the outer coat of paint, as well as some of the first paint layer, down to the bare wood. To tone down the contrast between bare wood and paint, a coat of oil-based wood stain was added to create a rich burnished look before sealing everything under three coats of spar varnish (tough enough for outdoor use). Be sure to do a light 220-grit sanding between each layer.