I had to think a bit too, but typically they are either straight out or, most commonly, out wide. He has just recently started sitting on his knees a lot, but that's pretty new.
I voted SS because depending on the activity or mood he sits differently. I can honestly say that he switches from sitting on his knees, to legs wide open, to the soles of his feet touching, to laying on his belly reading, etc. all day long. So a little bit of everything,
Re: How does your kid typically sit on the floor?
Even a minor event in the life of a child is an event of that child's world and thus a world event.