Ok, here comes the interesting part, not the hardest part, but the most interesting part. Getting all of the joints to line up and come together snug without a lot of slop was a bit of a trick. The bench has 22 sliding dovetails, two ends with half blind dovetails, and 8 through wedged tenons. They all have to line up pretty close or things wont come together square.
I started with the half blind dovetails on the ends.
This gave me the inside dimension from the base of the dovetails down the side to the shelves.
I used a Porter Cable 4212 Dovetail Jig to cut the half blind dovetails and the sliding dovetail dados. Here is a picture of the jig setup to cut a sliding dovetail dado.
The Porter Cable is a pretty common jig, not too fancy or flexible but it cuts a standard dovetail with little setup or trouble. It can also cut through dovetails, sliding dovetails, dados, finger joints, and probably a few other joints if you're creative, for a reasonable price and not too much fiddling.
After cutting the half blind dovetails on the end boards I setup and cut the sliding dovetail dados on the seat and shelves. I marked the edge of the dovetail dado referenced from the end of the self. I then transferred the mark to the mating shelf to make sure the marks were in the exact same place, and then used the mark to line up with the sliding dovetail slot on the dovetail jig.
To cut the dados I setup two routers, one with a 1/2 inch straight bit to hog out the bulk of the dovetail slot and one with the dovetail bit.
Obviously the dovetail has to be cut in a single pass at full depth. To ease the burden on the dovetail bit I first hogged out the bulk of the dado with a straight bit set just a smidge shallower than the final dovetail depth.
After that I just slid the shelf until the layout lines lined up with the edge of the dado slot on the jig and cut the dovetail dado in two passes, one pass with the straight bit and one pass with the dovetail bit.
The through wedge tenons turned out to be a bigger hassle than I had anticipated. Getting the through mortises clean and square without too much of a wedge angle turned out to be too much for me. The mortises turned out too big, the tenon wedge slots are uneven and at an angle. All in all not my best work.
I hogged out the through mortise with a forstner bit and "squared" up the mortise with a chisel. Squared is putting it politely.
I then chisled the angle for the wedge. It turns out the wedge angle needs to be pretty small. The tenon will only spread so much, in this case "so much" was not enough. I'm confident the tenons are wedged and are not coming out, but they did end up leaving a gap on the top and bottom of the mortises.
After that fiasco the rest was pretty easy. The dividers are all the same so I could cut the dovetails production style on my router table. Get it setup once and crank out all 4 cuts per divider.
I used the same dovetail bit moved from my portable router to my router table. I set the bit height to the same depth as the sliding dovetail dado. After a couple trial runs I set the fence offset to end up with a snug fit of the dividers into the dovetail dados.