My writing process is a bit different from my coding process with AI, it's more of an iterative refinement process.
I tend to form the story arc in my head, and outline the major events in a timeline, and create very short summaries of important scenes, then use AI to turn those summaries into rough narrative outlines by asking me questions and then using my answers to fill in the details.
Next I'll feed that abbreviated manuscript into AI and brainstorm as to what's missing/where the flow could use improvement/etc with no consideration for prose quality, and start filling in gaps with new scenes until I feel like I have a compelling rough outline.
Then I just plow from beginning to end rewriting each chapter, first with AI to do a "beta" draft, then I rewrite significant chunks by hand to make things really sharp.
After this is done I'll feed the manuscript back into AI and get it to beta read given my target audience profile and ambitions for the book, and ask it to provide me feedback on how I can improve the book. Then I start editing based on this, occasionally adding/deleting scenes or overhauling ones that don't quite work based on a combination of my and AI's estimation. When Gemini starts telling me it can't think of much to improve the manuscript that's when it's time for human beta readers.