Flat button knot. I made these from some scrap very fine knit fabric, cut about 1 3/4 inches wide, folded like double-fold bias tape except folded over one more time and stitched together into a nice smooth "rope." They look beautiful. It took a little fussing, but I think the secret is to pull up your knot methodically from one end to the other, and keep things laying nicely. They look really good on my new jacket.