Miris Dor, a Polish blogger shared his methodology of preparing a hexcrawl module (however it’s not that hexcrawley as you may hoped for as he reveals his philosophy in the second episode). It’s in Polish so if you’re not lucky enough to understand it you can run it through an automatic translation, it works quite fine.
What staggered me a bit is that it seems like a heckin lot of work. I believe I’ve been there at some point in my hexcrawl experiences but now I allow myself a lot of freedom and improvising. And I don’t think it’s a matter of being a good or bad DM but of grasping the concept that you actually don’t need a lot of prep to run a game which will be fun for all participants and you don’t need any particular set of skills acquired during a very long career to try it. It’s perfectly fine to stop the game for a minute or two to render another part of the setting. RPG adventures (please pay attention – not every RPG falls into that category) are all about participation and agency so it does not suck the fun from your game if you make up things on the fly. At least – that’s my philosophy and I’ll try to show you how it works on an example of a campaign which I prepared few days ago. It's not intended to be a guide but merely a collection of musings.