The best thing you can do to help format your own book is to pop into a bookstore that sells traditionally published books. Find several books in your genre and see what their interior looks like.
Your aim in doing this is to replicate traditional publishers and thus make your book look more professional. There are some things (such as embossed covers) that can’t be replicated cheaply, but fancy images for chapter headings can.

This is the chapter image we put at the start of every chapter in “The Odyssey of the Seven” by KJ Matthews. It was created in Canva (we love Canva for things like this). It adds a touch of “professional” to KJ’s books and is easily customised to her genre and series. When we look at formating for “The Odyssey of the Six” (due out Late 2023), then we will create an image that reflects that series.
This helps build a series and author brand. Both are highly important for marketing reasons.
That’s all for now, happy writing.