Okay, it's time to sew the lapped zipper. I almost always use lapped zippers in my dresses because it gives them that vintage look. Lapped zippers aren't difficult, but they do take practice. The more you do, the easier they are! I don't mark or baste my zippers. If this method doesn't work for you, there are many tutorials out there showing other methods.
Start by turning in and stitching the excess tape at the top of the zipper. You can stitch this by machine if you use a zipper foot.
Next we'll finish off the back neckline on the left side of the zipper opening. Turn the seam allowance to the outside of the dress and pin.
Now stitch across the seam allowance at the upper back neckline.
Clip into the stitching and trim the rest down so it looks like this.
Turn the seam allowance to the inside of the dress, forming a finished corner at the upper edge. Press this side of the seam allowance in 5/8" all the way down the zipper opening.
Here's a video to help you understand this step.
Once you've pinned, open the zipper again and top stitch the overlap side of the zipper at 3/8", using a mark on your needle plate to guide your seam allowance as usual (keep in mind that you may have needed to change your needle position for your zipper foot, so this will change the distance of your needle from the marks on your plate. Measure if you're unsure!).