Phew, that was a lot of work, and some things didn't work out the way I wanted them, but I guess that's to be expected with the first try on a rounded case book.
Cut the front edge (chisel ftw), rounded it (it felt weird to take a hammer to it, ngl), cut head and tail, then tried my best at backing it into a shoulder (not happy with that result tbh), then added a little book band matching the pink colour found on the official cover, black head bands and started building up the final spine.