You can fake a set-in sleeve by using any sleeve shape you want and inserting it into the armhole and add a soft sophistication to any garment by creating a sleeve that looks like it belonged there all along.
For this blouse, I chose a sleeve with a slight puff (as opposed to “pouf” which conjures up disturbing leg-of-mutton images from the 1980’s) is work appropriate while maintaining a floaty, ladylike charm. This technique works with sleeveless t-shirts as well.
For short sleeves, you'll need 1/2 yard fabric. Buy 1 yard of fabric if you plan to insert long sleeves.