Tours currently meet on the sidewalk in front of the cavernous (and we’re talking BIG cavern) main doorway to the Flood Building, 870 Market (between 4th and 5th Streets, a quarter block from the Powell Street cable car turntable — and Powell is a stop for Muni, BART, you can just roll in).
Stand where you can see the numbers 870 or the Flood building lettering as above. I’ll be outside on the sidewalk, waiting to see who shows up.
(The shot above is by Sue Montgomery, October 28, 2018 — the image that wasn’t photo-bombed.)
(The shots below show the Sisters in Crime assembling for a tour by appointment, August 5, 2017, and a couple extra of the walk in action:)