Most people who have sewn a dress of some kind, know that a pattern often calls to stabilize a neckline by stay-stitching. For a slightly fancier version you could use iron-on interfacing.
While looking for information on sewing silk charmeuse, I came across this interesting post which detailed a couture technique for stabilizing a bias edge. You cut strips of silk organza on the bias. Then iron them while stretching them out to remove all the stretch, leaving you with a very strong piece of silk that won’t fray.

I meant to show side-by-side the ironed bias with the unstretched one, but forgot. This piece started out as an inch wide.
I sewed the stretched out bias strips to the neckline, where it produces a very strong edge with little bulk.
While I doubt this is a vintage technique, it’s a pretty great couture technique which I plan to make use of in the future.
Bonus skirt picture! Here the seams are basted wrong side to wrong side, ready to be sewn down for french seams.
The tissue paper is pinned on and says “front” (or back, depending). Since the front and back pieces are mostly but not exactly identical, and I didn’t want to confuse them.