SewLibra:
McCall's 2401 provides facings to make a clean neckline like here on this V-neck version. But if your pattern doesn't have them and instead says to turn under and stitch, you can easily draft your own facings.
SewLibra:
The facings follow the neckline shape. The front is cut on the fold, the back in 2 pcs for a zip, but can be modified for the fold if no zip. Finished width is 1.5". Trace the neckline curves and add seam allowances for the neckline, shoulder, and CB.
SewLibra:
I used fusible tricot interfacing here, serged the edges to insure it stays on during the wash, understitched to keep the facing from rolling out, and clipped the curves.
SewLibra:
This one is a bateau neckline, Simplicity 1586, also with facings and a zipper. It looks so much better than folding under and stitching, especially on knits that could easily stretch out.
SewLibra:
The method is the same as before but these facings have a finished width of 2.25". Again, the neck edge is the very same curve as they made the facings. It's quite easy to duplicate using paper and basic measuring tools. A French curve is helpful!
SewLibra:
This knit dress has a back zip and I used a lightweight woven interfacing (out of tricot!). Same procedure of serging (or you can machine overcast) the edges, understitiching, clipping curves, and stitch-in-the-ditch at the shoulders seams.
SewLibra:
The Colette Moneta dress does not have facings with the pattern. Since it has a separate bodice, I cut out a second one of self fabric and used it as a combo lining/underlining. I understitched the neckline on this too, to keep the lining from rolling.