I'd already published five books, with the help of great editors, when I first heard of "islands." A writing friend knew I was struggling--a publisher was interested in my memoir and I had to deliver in three months. I'd honed my skills in nonfiction, even won some awards, but memoir is a whole different animal.
I was moaning to this writing friend about how to even get started, with such a deadline looming. She suggested I check out a book by writing teacher Ken Atchity. Called A Writer's Time, rereleased many years later as Write Time, the book was not at all about time management but about the two-part process of book writing. Atchity had noticed over the years of working with new authors that those who actually finished their books allowed random-access writing before any organizing happened.