I hardly know what this means. I used to draw a rough map if the story was a 'journey' adventure and made up the rest as needed for the story. My worlds are always inner (unconscious) worlds made manifest. I just learned to tap and shape that unconscious. I've never really understood 'world building' and it seems to derive from D&D etc. about which I know almost nothing.
I honestly believe this is what Howard was doing and what Leiber was doing. I grew up reading Freud and Jung (as it were) and I respond well to plots about people creating their own worlds in their minds. When writing s&s I made my landscapes and weather conditions fit the mood of the characters in straight Romantic tradition. Everything is co-opted into narrative and to a lesser extent character development. Realism or quasi-realism wasn't what I was attracted to in s&s and it's what I rejected in fantasy/sf. It became a convention to suspend disbelief by making the invented world as 'believable' as possible. I preferred mine to be as supportive of the story as possible and not bother to suspend disbelief because my readers already knew what they were reading and why. You don't have to persuade someone who has picked up a fantasy book that it is 'real'. What they want is a good story and characters, some good marvels, and maybe a bit to think about.
That's how you do it. I wrote a little about On Mighty Thews' map rules, which follow this process exactly, here.