Graham Greene set two of his novels, “A Burnt out Case” and “The Heart of the Matter” in Africa. The book, In Search of a Character: Two African Journals: Congo Journey and Convoy to West Africa, reveals the raw material — observations about people and the world — that eventually turned into his novels.
You're a writer. Do you journal?
If you don't, you should.
If you do, create a project journal for each book you write.
On some days, I spend more time writing the journal for one of my novels than writing the novel. That's fine. Your journal is a fun way of discovering plot details, character history and quirks, and structure.
Try dialoguing with your characters in your journal. You'll be surprised at what they have to say.