Notebook: Inspired by a photo of Benjamin Elbel's Dos Rapporté structure. Back made of paper-covered cardboard, front and back covered with an old and odd paper that I found.
A very crude attempt, to be sure, but it turns out to have the desired function: The hinges are offset from the spine, providing a lever effect that lifts the textblock upon opening. This in turns makes the book remarkably easily opened and flat when open.
Cf. Elbel, B. (2012). Dos Rapporté structures: Why consider structure? The New Bookbinder 32:17-22.