The Book says, “Most garments are designed with a set-in sleeve. This sleeve is sewn into a traditional armhole. The sleeve cap may be styled from a minimum to moderate to a great deal of fullness.”
A set-in sleeve begins with the sleeve already finished and ready to go, as is most of the garment it’s going into.
Crimp or Ease the sleeve. Here I’ll show you how to crimp. In the Shirt Sleeve lesson we’ll go over easing. Same idea, different methods.
To crimp run a stitch along the top of the sleeve cap, from notch to notch (assuming you’re not a dummy like me and didn’t put notches into your homemade pattern…) As you sew, keep your left index finger tight against the presser foot, puckering the fabric as it comes out after being stitched.
Now you need the sleeve right side out and the garment inside out.
Place the sleeve inside the arm hole on the garment, right sides together.
Match seams and notches first. Pin there.
Then ease the rest of the sleeve into the armhole, pining as you go
If you did it right, it won’t look like this.
Again: THIS IS NOT WHAT YOU’RE GOING FOR!
Unless you want it gathered, and then hey! Sweet gathered sleeve.
But really, take time and ease and pin as you should so that the sleeve fits in the hole better