Haha, wasn't expecting such a tip!

The problem is that if this plane is semi-stiff, it's hard to put your hand under it without making an opening between it and the glass. And that is not a risk I'm willing to take.

So the trick is that I slide something thin (the cover itself), but then can, as a second stage, put the rest of the book there, by closing it. But true, no reason those two layers must be a part of the same thing.

Today someone posted Show HN for a catalog of problems looking for better solutions. Maybe I should submit there?