Here's how I like to get the buttonhole placement on a shirt just right, tips on sewing buttonholes and a tutorial link to how to sew on a button.
How to position buttons and buttonholes? - Inseam Studios
Sewing Like Mad: Japanese Shirt Pattern plus Vertical Button
Shirtmaking: Buttoning Down the Basics EmmaOneSock Sewing Tutorials
Sewaholic Sewing projects, tips and inspiration for the modern
Sew Brave: Conquering My Fear of Buttonholes in the Quest for the
A Sleeveless Granville Shirt
Gamechanger tips for sewing buttonholes - Elizabeth Made This
Pattern Drafting A Buttonhole ~ Learn How To Create A Buttonhole
Sewing Shirts Skills Kit — Q & A series — In the Folds