One of my children is left-handed, so when someone asked a question about teaching a lefty to write at one of the HEM forums, I did a google search on the subject. It’s been years since my lefty learned to write and being right handed, I often wondered if I was a help or a hindrence as he learned. I found a site called “Handedness Research Institute” that offers a brief instruction for learning how to write left handed. I recall that my son learned in a way that was comfortable for him and is quite legible, but I did find the site interesting.
They point out that certain school desks are a challenge for a lefties in schools. There are also links to some good resources there under homework help and they also have an intersesting research section.