@ChrisseyWrites
Welcome!
Congratulations!
Kitties!
Bookbinding! (what are good options for a homemade lay-mostly-flat binding? coil binding seems effective but then you lose the spine and can't show the title when shelved. so many questions...)
Again, welcome!

@arclight
Kitty! 😍
So a "coptic binding" would lay flat. They usually have exposed stitching on the spine, but (although I haven't tried it) I think you can cover the spine so that you have somewhere for a title.
There's also "secret Belgian binding" (aka criss cross binding) that might suit your needs.
A hand-made hardback using a "case binding" technique will usually lay flatter than a commercial one but not like *flat* flat.
Have you done much binding yourself?

@ChrisseyWrites The only binding I've done is with PVA glue to make scratch pads. Not exactly professional or artisanal but it repurposed a ton of otherwise wasted paper at my last job. I have a technical manuscript that I'm slowly puttering away at; some people ask if I'd consider self-publishing and that got me thinking about how much of the production work I could do myself. :)