Indivious link https://inv.nadeko.net/watch?v=Is8N7B9b0GQ

TL;DR: His process is fascinating, he's made 4000 ~A4 panels that make up one giant continuous map with layers of what he calls dimensions. He used to keep track of population (through the city blocks he adds, towns have their own naming process, and some town were, I quote, eliminated by the void) as time that passes in his world. Every day he adds to this mega map by picking a card out of a customized 100+ cards deck that tells him what to do. He has systems upon systems for not only his process of mapmaking but also just making his world feel alive (he had in-lore sports team playing each other!!!). PMG - with Jerry's approval - then assembles the whole thing to see how it looks

his website https://www.jerrysmap.com/the-map

In the summer of 1963 Jerry began drawing a map of an imaginary city. The work started as a doodle done in the spare time he had while working at a tedious job. He continued to add to that map through the years until, in 1983, he set it aside to put his free time to other use.

It was stored in the attic of his home in Cold Spring, New York. It gathered dust. Jerry’s son, Henry, found it one day while rummaging around. He brought it down and asked what it was. Seeing it then triggered Jerry to dust it off and continue the project.

Years later, the Map is now a two-dimensional “virtual world” art project which is now comprised of over 4000 individual eight by ten inch panels. When assembled, these panels form an approximate circle. The panel locations are defined by N, S, E, and W coordinates that originate at the center of the circle. The locations in the matrix do not change, but the panels themselves are continually revised based on instructions drawn from the artist’s custom deck of cards.