I finally gave in and asked to copy the passage relating to the tutorial landform. I still don't know why I couldn't make something remotely like it, and it's driving me mad, but I have to progress somehow. So I copied it laboriously into another Book (fortunately the quality of the paper and ink seems to be negotiable, at least at this early stage--I would hate to think I was wasting a resource in limited supply) and found it exactly as it should be. I shall have to go back to the beginning again at some point. If I cannot create a landform the way I want it, my efforts are doomed from the start.
Unfortunately, my attempt to produce a small central patch of soil resulted in the entire landmass being covered with it. Not a bad thing, perhaps, but not the desired result.
I went back to Age Two (the one with the invisible walls) and put in a sun, having found that the tutorial landform came with one already Written in. It was nice to see myself at last. The walls, though, remained stubbornly black and featureless, even when I added another light source directly in front of each. What am I doing wrong???