When DS1 said his hands got cold trying to type in his office, I volunteered to fashion fingerless mitts for him. I say fashion rather than knit because I wanted to get them to him before next winter.
I took apart this thrifted merino wool sweater.
Then I measured his arm to where he wanted the cuff to come and unraveled the sleeve from the top down to two inches below that point 11" (13" finished). Then I picked up the stitches and knit 2 x 2 ribbing for two inches. I bound off in 2 x 2 on needles one size larger than I used for the ribbing to make it stretchy.
Next I created an opening in the sleeve seam for the thumb and reinforced it above and below the opening.
When I tried them on they were a little loose in the wrist and palm, so I turned them wrong side out and took in the seam allowance using a zigzag stitch on my sewing machine.