Iyengar writes that beginners should start Sirsasana in a corner so as to stay in alignment. My corner is -1.2ish degrees off from being perfectly level. I am wondering if this needs to be taken into consideration? My apartment is not the newest, hehe.
In some cases isolating a phrase or paragraph for comment strips it of its context. Iyengar writes many things relative to Sirsasana and begining students, and still other things on beginning students irrespective of Sirsasana.
I don’t think the slant of your home flooring is particularly relevant to the intended concept expressed by Gujruji (though I don’t speak for him). The two adjacent walls keep your legs from waffling in the breeze and allow you to find what is aligned for you relative to your foundation running from the outer edge of the pinky nails to the elbows.
The corner or “at the wall” is a good starting point for Sirsasana after the student has learned the movements of the shoulder blades via the contraction of the serratus anterior.