Important: don’t forget to trace all the pieces before making any changes to your pattern.
Draw a vertical line (parallel to the straight grain arrow) in the middle of the back piece (#2). You can find the middle of the piece by folding it in two so the sides meet.
Cut along this line: you’ll get the closed back piece, which you’ll need to cut on the fold in your fabric.
Similarly, draw a vertical line in the middle of the back facing (#4).
Cut along this line. To avoid getting a V shape at the bottom of the facing, tape it onto a new piece of pattern paper and extend the center back line. Draw a line perpendicular to the straight-grain arrow at the lowest point of the facing, meeting the center back.
Cut your new back facing along these lines. You’ll need to place it on the fold as well.
Be careful, if you make this change to the pattern, it is very important not to size down as it is possible to do on the wrap back. The extra ease given by the wrap is not there with the closed back, so it’s especially important to follow the measurement chart.