[frahse]

Remember an outline is what you make it.

I look at it like a bunch of boxes and circles and there are things here and ideas there that you want to reach. You can draw lines from one to another or not.

You don't have to start with a flow chart or a project managers outline. You start with a few ideas and then as you go alon(g) you write down some salient facts and ideas in a place you can find them later, and then you start sorting or collecting these things.
If you try not to put down anything except the text of your book in the published sequence, you will slow yourself down because you will have to go over and over those ideas in your head or you will have to (and I use an old phrase here) do a lot of erasing and rewriting. Later or course it was whiteout. Now of course it is digital.

To summarize, as you write put down what you want to do, and then write some more and repeat. You will be writing and outlining all along at the same time. There is no need to worry too much about what comes first. You will realize after a while what you need and when you need it.