Sorry for the photo quality. Screaming red is difficult to capture at night.
So here is my son's sweater knit to the shoulders with a kangaroo pouch* at the armhole. One of the shoulders has been bound off. Normally the "pouch" would be a bit bigger but this is bulky yarn and a small sweater.
I did a line of basting in cotton so I could see where to machine stitch.
After machine stitching up both sides of the basting I am ready to cut.
The stitches around the armhole have been picked up and I am knitting my sleeve down.
When I finish my sleeve I will steek the second armhole and repeat. Then I get to cut open the front of the sweater! Steeking is fun.
*A few stitches but on a holder with steek stitches cast on over them. The sweater continues in the round and the armhole is steeked.