Oooooh, bookbinding thread! \o/
Not June, but from the picture I’m guessing it’s Coptic style binding? The cover is cardboard or maybe some kind of watercolor paper and sewn together with the signatures.
Here is a video by DAS bookbinding showing how it’s done:
(Sewing starts at 15:58 and shows how the cover is connected to the signatures.)
These are amazing! I’m definitely adding bookbinding to the list of things I want to learn how to do. I find that I just don’t use pdfs. Running games from them doesn’t click with my brain, and I’d love to give my pdf library a chance by making some of those things physical. If anyone has a “bookbinding for beginners” video or article to point me in hopefully the right direction, that would be amazing.
Watching Sea Lemon and trying to copy her hand movements are how I started. I’m doing some stitching today, so I’m watching her again to refresh my memory. Haha.
That sounds very do-able (she says before seeing the actual videos 
). Now to decide my first thing to try out.