I didn’t have any cording, so I made my own using some cord elastic and a strip of fabric, using a zipper foot. You can use a lace or something similar to make your own, in a pinch.
Sandwich your cording between the layers of fabric, right sides together and selvage edges lined up
Use either a cording foot (which I didn’t have) or a zipper foot (which I did) and stitch along the edge of the the cording on the seamline
The Book just leaves you hanging there. But I’m assuming you should press seam allowances flat, so I did just that.
I’d probably also trim things down on a real project.
The Book says: “A Corded Seam is a decorative seam or edge and can be used as a design feature on a garment.”
I’ve made pillows and started a kid’s reading chair that used this cording seam, too.