Abby from Things For Boys shows how you can add a button placket to the back of a shirt. The placket creates a larger opening so the shirt is easier to pull over the head. It works for t-shirts and knits, as well as shirts made out of woven fabrics. Her tutorial shows her adding one to an already made shirt, but you can easily incorporate this into the construction of a shirt you make. Get the how-to.
[photo from Things For Boys]