When I see the term “world-building“, I usually think in the grand scale. And by that I mean maps depicting countryside hundreds if not thousands of miles across, vast mountain chains, entire river systems, cities, broad cultural swathes, and on and on. I expect most people probably think of it at that sort of level.
I’ve been world-building since high school, perhaps even before that. It would usually start with a map, generally a coastal map. In sharp pencil. There was usually lots of rubbing out and re-drawing. Those that lasted a while generally acquired a corresponding computer file, describing cities, races, countries, even languages and history on the more complete ones.
And then I started writing stories in them.