Prepare back pieces.
Sew darts using either elastic stitch or zig-zag for knits:
Press darts in the shown direction.
Pin back pieces together in center line.
Lay zip and note where it ends, a little above the end of the zip.
There is a method I prefer for invisible zip insertion. The next steps will show you the method. If you have another method, please, go ahead a few steps! So, what I do when sewing invisible zip: I sew with usual stitch ( in this case elastic or zig-zag for knits) from the marked zip end to the bottom of the skirt – red interrupted line that you can barely see it is interrupted; but, the key to a successful invisible zip insertion is to stitch where the zip will be, with a straight big-step stitch, that later we will unpick – the red interrupted line.
Now press the seam open.
Lay zip on the pressed seam. Check the teeth of the zip to follow the seam line. Pin and then hand baste the zip to the seam allowance only! Do not hand-baste to the back part.
Turn the back piece to face the right side of the fabric. Unpick the seam only on the zip part.
Take off the threads from the unpicked seam. Open zip till the end.
Move zip holder as far down as possible.
You should have some space between the holder and the seam end of the back.
At this point you have a hand-basted zip. Move on to sewing your zip on your sewing machine. Use zip foot or special invisible zip foot. In my case, I use a simple zip foot. Sew with a normal straight stitch, not the elastic or zig-zag:
Now your zipper is hand-basted and machine sewn at the same time:
Serge together seam allowances and zipper.
Now your zipper is in place. Take off the hand-basted thread and press gently the back seam and the zipper. Press on both sides: on the right side of the fabric and on the wrong side.
