I am going more to Xeric plantings, which often are some assemblence of ground cover, low growing sprawling things. I started doing something similar, sort of accidentally. My WS seeds or seedlings I plant in the round ice cream containers from lets say Dryers and poke some holes in the bottom or cut slits, bury them a little, put the soil, some gel crystals and water them every few days. What I found is that they hold the water better, with the wax carton and the bottom breaks down first, so the roots just keep digging deeper. The ring, of the carton seems to be of similar dimension to your rings according to size. By the time the carton is rotting, I just peel off the top part of the carton and throw away, the plant is nicely and deeply rooted and needs to be watered much less than it otherwise would have using other methods. Less disturbing the tender plants too.
You are quite a mathematician lady. I admire that. Cool idea. I am in the west so it makes sense here.