Although I love being able to break "Earth rules" in a truly fantasy world, I find it's easier to set my fantasy on good old planet Earth, in exotic locations. The distances and basics suddenly write themselves! Of course, I still can't decide which island and town my MCs hail from... and that will matter in the long run... but at least I have a starting point.
My current WIP is set in the Orkney Islands, Scotland. I visited last year... of course, I've been smitten with the islands for years now. I first read about them in Mary Stewart's Merlin novels... then in T.H. White's Once and Future King... and then when I looked them up, I stumbled on Orkneyjar, the most rich and fascinating website! I've spent hours falling down rabbit holes and following my nose... and the research that I've done has really helped me to see the settings I'm trying to write about.
The Orkneys really are thrilling, beautiful, and full of folklore. Who could ask for a better setting for a fantasy? And then! Something amazing like this happens. I could've made that up, but having it be REAL is so much more exhilarating! Don't you think?
What do you do about the details of world-building? Does it come easy to you?