I have been dying to learn cord binding and am having no luck with anything on the internets. I did find a video tutorial on embossing simple designs onto leather bound books and that was close enough. These are actually upcycled. I got some kid's board books from the library when they were giving them away. I peeled off the shiny parts and then took a sharpie and drew an image onto both pieces. I then took some linen yarn and glued it onto the lines and after brushed on some watery glue. When completely dry I brushed on more glue and placed a cut up brown paper bag piece on top. Over about 45 minutes to an hour I burnished the image with my bone folder again and again. I would push out the centers and then up against the sides until it was dry enough to take the shapes. This is the front and back covers for books not yet bound. Each one took the almost full hour. When that was dry I painted on several layers of acrylic paint. Lots of work but completely worth it.
This was my 2nd attempt at embossing designs onto a book cover and then completing the book with longstitch binding: