I saw that episode on TV. Cool. Thanks for posting this. I had to do some circular decorative stitches for homework for a quilt class I took. I used a command strip and drew lines half inch apart. Stabilized my fabric. Took a sturdy straight pin and poked the pin through the center of the fabric then stuck the pin on one of the lines and sewed a decorative stitch. It was awkward but did a good job. Also used the open toe applique/embroidery foot. It's slick on the bottom. I suppose if I had to do a lot of these circles, the actual attachment would work better. But, I could not see myself doing that so I save some $ for fabric.
Oh, I used one of my rulers and lined up the command strip to the left of my needle. Changed the thread for each stitch and shifted the pin a half inch for the different stitches.