I wrote a story in a setting that I was unfamiliar with. I'd probably seen a film set there, read a book or two in that location. But it wasn't somewhere I knew. I allowed my imagination to fill in the gaps and created my own setting. Unique, if not completely accurate. But so what? I didn't ever state where it was supposed to be. It's my place. Things took place there that I don't have first-hand experience of either, but the story won a competition. So the characters, plot and setting must have worked well, despite my fumbling in the dark.
So I remain a bit confused about the notion of wriitng what you know. It worries me that writers restrict their minds when planning a new story. If I develop a suddden interest in the Australian outback, even though I have no knowledge of it, I might plough into a story set there. My ideas will come from the smattering of information I possess, plus a tiny bit of research. I still won't know the Outback will I? But my story could still work well.