My stylish coworker came in one day in a striped top that offered a neat twist on the basic Breton tee: Each long sleeve was embellished with a flounce that wound from top to bottom, on a diagonal. The flounce was incorporated into a single seam, spiraling around the arm. Each sleeve was cut as a single piece—but we could tell it was an unusual shape.

We immediately set ourselves the task of re-creating this sleeve from a basic pattern. It looked difficult but turned out to be simple. The pattern work and the sewing are surprisingly straightforward. This method works for knits or wovens. We show it with three wraps, but you could plan a spiral that corkscrews around the arm many more times. Insert a flounce or other trim, or add topstitching to enhance a plain seam. Experiment: It’s less convoluted than it looks.