So I attacked the sashing on Tuesday and even though it was only 4 little strips I was so glad to finally get it done.
And amazingly, by the time I did the last two I didn't hate them. I actually kind of liked my crazy idea of making and cutting the sashing in bulk. What was really nice about it was that the sashing strips were nice, clean, fresh-cut edges all along their length. I think that made a big difference in their attaching enjoyment. And I even had to smile at doing the easing.
Several of the cornerstone blocks ended up looking like this. Nice and square. I may actually do a bit more sashing now!