I used to be so intimidated by this alteration, but it really is simple and the more you do it the faster you’ll get.
1. Pin the pleats down then remove cuff, placket button and placket.
2. Measure the amount you need the sleeve to be shortened, then cut on the mark, removing the excess. I’m removing 5″ then measure up from the slit, the amount equal to the amount you removed. I removed 5″, so I have to cut up 5″ from the top of the slit.
3. Put placket back on, starting with the small piece. The small piece is attached to the part of the sleeve closest to the back of the shirt. Be careful how you put it on. The back or the under side of the placket will be wider, so that when your sewing it on, the underside will be caught in the stitching.
Now sew the large piece back on, making sure the smaller piece is not visible,when it’s sewn on.
The front of the cuff is interfaced, but the back isn’t, so it can be a bit floppy. Sew with the interfaced side up, so the feed dogs will feed the “floppy” fabric through.
When you move the cuff up that much, you’ll need to add another pleat, on the other side of the placket. Just make sure, the tuck is facing the right direction.
5. Sew the placket button back on.