The case/cover starts out with carefully-sized binder board. The width of the spine strip matches the thickness of the book block. The front and back covers are cut to leave a 1/8-inch overhang around the edge finished book. Each piece is glued to heavy craft paper with a 5/16-inch gap between the pieces.
When the glue on the initial assembly has dried, a strip of book cloth is centered on the spine. Here, hinge gaps are clearly visible, having been pressed in with a bone folder. This will be the 3.5" x 5" notebook, seen below.
Decorative cover paper is added, leaving an inch of extra material to be folded inward, later.
The extra paper is folded in and glued to the inside of the cover panels. Work on the little, green notebook had progressed a too fast, and I forgot to photograph it at this stage. Shown is the case for a 5" x 7" Arthur Conan-Doyle book I've been working on for my personal collection.
The black book cloth used on the spine and the headbands has no paper backing, making it hard to handle. I decided to use it on a personal project instead of for customer work.
Here is the finished, green 3.5" x 5" notebook with a 5" x 7" one in red. There was a black ribbon added to the larger one for a bookmark.
That's about all there is to it. The whole process takes about two days, and most of that is waiting for glue to dry. With a bit of forethought, I can stagger the steps so that more than one book can be in-process at one time.