It's not an issue of there being a physical map present. I'm fine with those. Ursula LeGuin, my favoritest Fantasy writer, has maps in her Earthsea Series.
But what i gathered (perhaps erroneously) from the phrase "paint a map" associated with the other comments, was doing it via prose. My caution there is that doing a heap of prose "world-building" dissociated from actual story, is a killer for me as reader. This view stems from experiences with a writer's group some years ago in which two of the most active participants did absolutely nothing but "world-build". For some aspiring writers I think this can get to be a poisonous trap. At worst, it actively interferes with story development, and becomes a huge obstacle to producing reader-attractive work.
If you want to have readers for your work, you need to think beyond "this is what I like to do," and think about "what will readers most like to read?"
caw
On this, I agree, as I've suffered from this myself. A good novel is the blend of setting, story, and characterization. The key is to create a sort of feedback loop where each of those things feeds into the others and becomes stronger for it.
I used to try to build a world, then struggle for a story. Now, I start with an idea for a world, an idea of the story I want to tell, which then leads to the characters who will drive the story (be it "a farmboy with a Destiny" (which would require the world to have farms, boys, and some sort of predestination), or, as in my current WIP, "an ancient tree-being encased in stone, worshipped as a living idol by a tribe of subterranean snake people," which would likewise require all of the above). From that idea, you flesh out the details of the world, which would also give you an idea for subplots, which feeds into the story, which then needs characters to drive it, and so on.