Writes a file into exports/. The world itself is not changed.
exports/
Made here, in your browser, as a file to download. It goes where it is on the map, at the same height: the flat world's grass is at y 63.
Puts the plan on the Minecraft server through the mc-roads mod, keeping the 16×16×16 sections it writes into as they were. Taking it off puts those back exactly, with whatever players built in them since.
Kept in this browser, for every world.