The pieces were first hand stitched together along the stitching lines, and eventually machine stitched into place. (And then those pesky basting stitches were pulled out.)
It definitely gives a basic idea of the garment, but nothing is pressed down until the seam lines are finalized and stitches are set with steam from the iron.
The challenge with this bodice was all of those points and internal corners at the hipline. To stabilize those spots, I used scraps of silk organza.
I really don't know what I did before discovering silk organza! This stuff is magical!