Thanks for all of the replies, especially the longer ones.
I have a Charles Dowding book (see next paragraph) and I'm waiting on a Ruth Stout book.
I don't want to put in unknowns which might have synthetic chemicals. Cardboard: I'm not going to use cardboard, newspaper, or other manufactured stuff. I watched the first five or so minutes of this video (
https://youtu.be/X7iFHnsh6Y4). Hay/straw/manure: I'm leaning heavily against using it, too. Someone somewhere warned that their garden was damaged by synthetic chemicals after a few years of using materials that were said to have not been sprayed.
I'll consider and am leaning toward wood chips from a tree service. And leaves. Those should be relatively free of synthetic chemicals, no?
What about using the lawn? In the two years I've been here I haven't watered it, it grows in spring and loses its green in the summer heat (it seems like that heat has started early). The lawn is tall and is probably various grasses and weeds. There are some nice small flowers in there. Since I'm still deciding and starting small, I'm going to experiment.