I used (just) two NBK products.
Process Notes here: https://ozone.oscraps.com/gallery/showphoto.php?photo=385124&title=process-notes-for-january-mountains

The quotation is Ursula Le Guin's translation of Lao Tze's "The Wheel," which I saw in a lesson plan about notan, a Japanese word meaning "light/dark" (balance). Notan is often presented as a papercutting exercise starting from a black square, but of course, the concept of dark-light/pos-neg space applies to art in general. Link to lesson plan, for those interested: http://www.dentonisd.org/cms/lib/tx21000245/centricity/domain/932/notan.pdf

Thirty spokes meet in the hub,
Where the wheel isn't is where it's useful.

Hollowed out, clay makes a pot,
Where the pot's not is where it is useful.

Cut doors and windows to make a room
Where the room isn't there's room for you.

So the profit in what is
is in the use of what isn't.

Here's a less mysterious translation by Gia-fu Feng and Jane English:
Thirty spokes share the wheel's hub;
It is the center hole that makes it useful.
Shape clay into a vessel;
It is the space within that makes it useful.
Cut doors and windows for a room;
It is the holes which make it useful.
Therefore profit comes from what is there;
Usefulness from what is not there.