I have no idea how it worked, but I started off just knitting in the round. I had a circular band about an inch wide. The next step in the pattern said to cast off half of the stitches and.......voila! I had tank top straps! So cool!
So, here's the front and back of the top of the bodice so far:
See my original post for starting this for details on the pattern, called Eden's Adam.