I suppose it might interest readers to know that there really is a Sand Pond, and it really is a place of magic, even today. It's also true that I worked as a laborer, even as a very young child, in the tobacco fields still common to Lafayette County, Florida. The acknowledgments in the book give a very good idea of the research required. It took a lot. If I'd know ahead of time how much work it would take, I'd probably not have attempted it.
Successful writers use both methods.
But it is definitely true that the present cultural exhortation of spontaneity over planning gets embraced by many writers who would rather type than think. An emphasis on any Muse that ignores thought or preparation is either slothful or disingenuous. James Joyce , for instance, is almost always described as writing spontaneously. But Joyce painstakingly collected notes for, and outlined, his work. We have Joyce's outline for Ulysses .