I did it! I made my first coptic stitch book and had a lot of fun with it. I did make some modifications from the course instructions though.
My intentions for this book from the start was for it to be my sketchbook and so I used a thicker (65 lb or 96 g/cm^2) sketch paper. The size of the individual sheets was 9" by 12" so the dimensions of my book are a bit larger than in the instructions. I also used some waxed bow string instead of bookbinding thread which did not work out so well because the thread itself was not black, but the wax was black. This kind of made a mess on my pages around the punched holes as the wax got smeared around when the thread was pulled through. Oops. I will order some actual waxed book thread for my next bookbinding project.
I also made the binding way too tight so the covers do not lie flat, but hopefully over time, the thread will stretch and relax a bit. Overall I am very happy with it.
Here are some more pictures of my finished book!
The paper for the end sheets I used were very difficult to work with once glue was applied as it because very weak and was about to break apart. So I found it easier to apply glue to the insides of the covers and only the edges of the end sheets.