The back wall was pretty straight forward. Because I'm going to have a drop ceiling in this area, I planned to run the stud walls less than full height. This made building a lot easier (and quicker) because I could just cut to length, build on the floor and tip up into place. Once positioned, I glued and nailed into the concrete and then created ties into the joists to locate the top plate plumb.
The partition wall was a little more complex because I had a shorter section to run under the duct, then back to standard height for the remainder of the wall.
I centered the door in this section, leaving about 25" between the door frame and the back foundation wall. This will be perfect for 24" shelving in the unfinished space.