Another suggestion was to go ahead and make boxes, even if the joints aren't perfect. I had been shying away from this approach, valid as I think it is, because I don't always have time in the shop to do multiple joints at once and like the sense of completion of these little individual joints. It was also suggested that I actually glue the joint, as the glue can affect the final appearance in a few ways.
Well, yesterday I did go ahead and make a box carcase, and used a square to ensure that the floors were flat. Still not perfect, but definitely a bump forwards and with my "dovetail month" total now at 20, I feel pretty good about where I might be with 11 more. Maybe we'll make it 12 more, for 3 more boxes. I feel like this one is actually good enough for shop use or a gift to a family member (the type who would frame my childhood art class disasters and proudly display them).
I do have to admit to cheating here though: the joints have only two tails. I am not sure if this reduction in number of joints is the reason for the sudden improvement, or if its the above. I'll resume 3 and 4 tailed joints next, but it is nice to have something go together fairly well. The shoulders one the tailboard (or the half-pin sockets) give me the most trouble. I use the dovetail saw to make them, and start the cut in a chisel V-groove cut out of the knifeline. The dovetail saw leaves a bit of a rough surface, and I think my attempts to smooth it introduce roundness. Perhaps my sawing technique needs to improve, or perhaps my chiseling does more harm than good. I'll keep working on both.
The box is made from alder milled from a tree in a neighbor's yard. I saw this tree when it was a log sitting next to the bandsaw mill. Its quite satisfying to dimension and true it by hand, and cobble together something resembling an artifact from it!