I can tell you something that is working remarkably well for me, and entirely by accident: I had a sketch of a campaign world I wanted to build, but only 1 small area that was solid. It languished for a couple of years.
Then I got introduced to a website where people publish serial novels (Royal Road).
A few months later I had a bunch of story ideas bouncing around in my head, and a particular combination was demanding most of my attention, so I started writing it. I'm a bit of a 'panster', so I just started with my opening scenario and wrote.
But I found myself needing information for the world around them really fast, and then realized I had a solution: It fit perfectly in the campaign world I had started. This means that to keep writing the story, I had to keep filling out details that could be added to my campaign website. I also have two other story ideas I have started to sketch out that help fill details on other continents.
In short: If you can write a story in your campaign world, then answering questions around that story will give you campaign details.
Important note: The story you write IS NOT and WILL NOT be the adventure your players go through. Ditch that idea immediately. The story is its own thing.