To make these take your basic sleeve pattern and then make three slits in your fabric. Next take your contrasting fabric and then cut segments sew them together so now you should have elongated sleeve pieces. (I like to use a poofy/gathered sleeve pattern as my base but if you don’t have one before you cut the main piece you can just add a few inches in the middle (basically elongating it so there is room to gather) before you cut the main piece).
Next fold back the contrasting segments so that the main colored fabric touches and the contrasting colors are folded on each side i.e. box pleat and pin. Sew across the top and bottom to secure the pleats.
Run basting stitches along the top (rounded) edge of the sleeve pieces. If you are finishing the sleeve with a band then run basting stitches along the lower edge as well