Reddit mentions of The Geometry of Hand-Sewing: A Romance in Stitches and Embroidery from Alabama Chanin and The School of Making (Alabama Studio)

>Do you think it's possible for me to learn hand stitching online, though?

I think so and every decent beginner or reference sewing book illustrates stitches. Here's a guide from a tailoring forum on how to practice. Here'sanother book you might like. But it's always better to have someone experienced look at your work. For example, I took a class that had some hand sewing exercises and was convinced that I'd followed the instructions to the letter. I was very careful and slow. The teacher told me that they were too tight. There are things that you simply won't pick up on if it's just you and a computer monitor.