Set-in sleeves are kind of tricky, and there is an easier method.
This method is still good to know, because you might find yourself in a situation where you want to modify/add sleeves to a top that already has the side seams sewn up, or doesn’t have side seams.
Here we go. We’re starting with the side and shoulders seams already sewn, so we have a basic sleeveless top. The sleeves have also been sewn up and cuffed.
You can ignore the hood in the bottom right hand corner. That’s for later.