There seems to be an impression out there that writing a novel organically takes longer than writing one using an outline. Some people outline their books and go through dozens of drafts; some people write organically and hardly have to edit the manuscript at all. Some of it is skill, artistry, intuition.
Writing great fiction takes a lot of time no matter how you approach it. I’ve had a number of professional novelists confess to me that the more they write the less they outline, simply because they don’t have time to write detailed outlines and still meet their deadlines.
Writing organically doesn’t mean approaching a story with a blank slate in your brain—you know about story, about genre conventions and reader expectations. If you’re writing a series, you’ve made promises in previous books that readers will look forward to finding payoff for in the book you’re working on.
If you ask the right questions and let the story continually unfold before you by letting the narrative forces press in upon it, you’ll be able to write the story much quicker than if you were to outline it and then have to make edits because there are continuity or causality problems.