From The Inside Out: Worldbuilding Through Extrapolation
by Suyi Davies Okungbowa
It’s virtually impossible to do ALL of your SFF worldbuilding prior to writing your book/story. How much weight is given to each stage depends on the author (some prefer to do a lot before starting, some build nothing before writing). My own preference is to build the foundation–just enough to get me started, then build more along the way, and go back and change stuff after I’m done.