My mother asked me to make her a one-of-a-kind diary in A5 format, but with lined paper. This meant I could not use the blank paper I have been using for my small notebooks. I solved this by buying a cheap diary and stripping off the covers. Then I picked the signatures apart, with the inevitable loss of one sheet of paper from each signature due to the outermost sheets of each signature being glued to the next signature. The paper in those books is very thin, so I added an extra sheet of heavier paper to each signature to protect the spines (in the future I may just guard the spines of the signatures with strips of paper instead of adding whole sheets to them). Then I sewed the block up on ribbons and added colourful endpapers:
I reused the old boards to make the new cover, stripping off the black paper and the red bookcloth nearest to the spine and covering the boards with scrapbook paper. I left the red corners, which harmonised nicely with the warm browns and oranges of the paper, to show the book's origins. I then glued the boards down onto the endpaper and glued the two shorter lengths of ribbon onto the boards for extra strength. I also added some glue to the spine to hold the ribbons in place and fill in the sewing holes for extra strength. The longest ribbon can be used to tie the book closed.
I am still perfecting the technique. Because I have no book-cutter (guillotine) to use at home the edges of the pages are inevitably uneven, and because I have to cover the boards before gluing them to the textblock, I have to be very precise both when I cut them and also when I place them so that they are not uneven and the textblock doesn't stick out from the covers. But on the whole I am rather pleased with the result.
The next step will be to try ornamental stitching on the spine.