From the David Minter article "Faulkner, Childhood and the Making of The Sound and the Fury" in a 1979 issue of American Literature:
[Quoting Faulkner:] "One day I seemed to shut a door between me and all the publisher's addresses and book lists. I said to myself, Now I can write" – by which he meant that he could write for himself alone.
Almost immediately he felt free. Writing "without any accompanying feeling of drive or effort, or any following feeling of exhaustion or reflief or distaste," he began with no plan at all.
He did not even think of his manuscript as a book. "I was thinking of books, publication, only in...reverse, in saying to myself, I wont have to worry about publishers liking or not liking this at all."
Then he wrote this.