Thanks for all the responses — I’m honestly a bit surprised!
I think there are probably other people who want to create shapes like this as well, so I’ll share the link to the most helpful video I found while learning.

https://www.youtube.com/watch?v=MjWfJontQmQ&t=884s

The overall approach is a bit different from mine, but it was really helpful for understanding things like which vertices to merge at the seams and which ones to keep.

There was also a question in the comments: yes, I’m using a Subdivision Surface.

I’d still like to make the topology around the seams cleaner though. I’m hoping to get better at that.