I turned the light blue sweater inside out and then machine sewed a line from the top down about 3" in, and about an inch from the edge, for the thumb. I hand embroidered these pieces before wrapping the cuff around them, and hand stitching with a cross stitch. I then added 3 of the buttons.
The darker sweater had these funky cuffs with covered buttons. I chopped about 8" off of the light sweater, and chopped the whole cuff, about 9" off the other. Then removed the buttons.
This instruction idea can be used with many sweater pieces. For sizing wrap a rectangular piece of sweater around your arm to see how wide and long it needs to be. Try several types of textures, and more than one or two colors. This is freestyle sewing, there really isn't a pattern, you gotta just go with it!
These are in my store.