Basement reno question(s)

Hi all, redoing basement bathroom. When I build/install a wall parallel to my floor joists, which is the best way to block it?
Top still plate of wall will sit approx 6" below bottom of joist. Also where it meets up with existing exterior wall, there is no stud due to spacing. Should I block between joists flush? Then my wall would have to have a cutout in it (if that makes sense).
Or block down the 6" from bottom of joist? Hope this makes sense.
I have to block due to hydro water and ng.
Oh also should blocking be on edge, or on it's back?
Thanks all.

20181020_212928.jpg

20181021_190109.jpg

20181021_190127.jpg

20181021_191401.jpg

20181021_191450.jpg