A couple of points:

(1) Indeed, many times during the instruction process I found myself thinking "I wish I could just experiment!".

(2) However, there were at least two specific pieces of verbally communicable non-obvious information that proved to be crucial: (a) the idea of putting one's finger on the side of the book near the spine to detect the pressure of the blade and thus determine that the book is in place; and (b) the idea of preventing dislocation of the book simply by cutting sufficiently quickly. I'm not sure I would have discovered these things myself very quickly at all.