The spots where the arms drop onto the front legs are subject to any tuning that must be done at the joint to the back leg, so they are not selected until that work is complete. I tried to get them as symmetrical as possible before glueup. It turns out I could have done more shaping where underarm meets leg (imagine that! No, don’t!).
Here I was careful to select similar grain patterns on the top (not shown).
Mockup with back parts:
It looks to sit properly vertical at rest and the back slats have delightful springiness. Note also that there is an even number of slats, meaning that your spine does not fall right on a hard surface. That’s a nice feature, clearly putting comfort above aesthetics.
From the assembly narrative, I learned a new word: arris. It is the point, usually on moulding profiles, where two surfaces meet. The instruction was to “remove the arris where the back rail and side rail meet the back leg.”
Next: some more assembly.
-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"