You still have to write your sample chapters, come up with a marketing plan, compose a full bio on the author, and write summaries for each chapter in your book, but at least you have a game plan laid out for you when using Carolyn's example.
If you create your book proposal before you write your book, you will have a solid outline to use for writing the book by the time you get the proposal done! And, the overview you write for your proposal, may very well make a great introduction for your book. The cover letter you send with your proposal can provide material for your back cover blurb!
Give it a try! Write your own book proposal using Carolyn's 49-cent Amazon short. If you get stuck, you can always have Writers in the Sky Creative Writing Services assist you.