I've been self-publishing books on Amazon since 2015, writing 12 books in the last four years, and have made almost $108,000 through Kindle, paperback, and audio versions.
The first hurdle to self-publishing is that people don't understand how much goes into this business. They underestimate the number of roles you play.
Here is where you're going to think of the transformation you want to deliver to your readers and maybe help them realize a change you achieved. Then you develop your idea, working backward through every step they need to follow to reach that end goal.
Once you've developed your idea, write out the main topic or step for each chapter and create each chapter separately. So this means the same process, thinking backward from the result to everything they need to learn to move on to the next chapter.
With your chapters outlined, you can move on to writing the book. Take it one chapter at a time, maybe one chapter a week. Then it would help if you had a developmental editor, and this is one of the most self-published authors miss.
What a developmental editor does is check the book for ease of reading and flow of information. They're going to make sure the layperson that knows nothing about the topic can go from page one to page 100 and achieve that transformation.