In the next steps we will be working on the neck shape. For the neck we will use facings. Interface your pieces:
Sew back facing pieces to front facing piece on the shoulder lines. Press open and serge outside:
Pin the facing to the dress:
And machine stitch with normal straight stitch:
What I also prefer to do, is to serge it, although this is not mandatory.
Before turning the facing, we need to cut just a bit on some areas. We do this because our seams are curved and the facing must take the round shape. Cut where the zip ends as shown in the image.
Cut just a bit around the shape. Your cuts must not reach the stitch for at least 2 mm. If your seam allowance is less than 5 mm, you probable can skip this.
Turn the facing. Hand-baste 5 mm from the edge. We do this to fix the facing for pressing. My baste thread is a pale pink barely visible, but you should be able to see on zoomed pictures.
Also, pin to fix shoulder facing seams with the dress shoulder seams:
Stabilizing the facing to the dress. This step can be done in various ways. You can hand-sew the facing to the seam allowance of the dress. But I prefer to do this with the sewing machine. Here is how. Having the facing hand-basted and pinned, turn the dress so that the right side of the fabric faces you. We will make a small stitch right in the shoulder seam. The seam should be as long as to catch the facing:
Where my finger lies is the neck line. What you see is the right side of the fabric. The facing is underneath. Do this for both shoulder seams. Here is what you get: a very small stitch visible on the facing, but barely visible on the right side:
This way, the facing won’t flip around when you dress yourself up. It was fixed on the shoulder seams.
Now press and steam the facing:
Take the hand stitch off, and press again. Your neckline is done, you can close the zip now.