The center-back seam allowance of the skirt is never pretty. The skirt gets lined, usually in beautiful contrasting fabric that flashes when the dancer kicks, but the bulky seam allowance always stands out, looking gross and un-finished. Due to the way the skirt is constructed, and the fact that the center-back is an alteration point, there is really no way to hide the seam allowance completely, so I like to bind the center-back seam allowance in lining fabric. You can do it two ways:
1. Leave extra seam allowance on that edge when cutting the lining fabric. To figure out how much lining seam allowance to cut, double the seam allowance of your other fabrics on that edge. So instead of 1″ you’d cut 2″, or instead of 3″ you’d cut 6″.
Press over 1/4″ of the lining and fold it up and around the edge of the skirt panel to the top. It should end up about 1/4″ away from the center-back seam line. Don’t let it sit closer than 1/4″, as you don’t want it to interfere with the seam. Pin the edge down as shown below and stitch along the edge.
2. If you’ve already cut out the lining and weren’t able to add an extra inch or two, you can also just cut a strip of lining fabric and bind the edge in the standard way, like you would with bias tape…really really wide bias tape! Except it doesn’t need to be cut on the bias, since you’re binding a straight edge. Just like in the previous description, don’t let it sit within 1/4″ of the seam line.
If you ever need to let the center-back seam out, the wrapped fabric can just be folded back or removed completely.
Here are a few photos of a dress from a couple years ago. This one was done with the second method of using a separate piece.