There are 2 issues here.
The first is you can’t give advice when you don’t know the basics yourself.
The fact you’re asking about how to create a character means you don’t have the first idea about writing novels.
And that brings up the second issue.
Until you have a reputation for writing quality novels, no-one is going to read a book on how to write them by someone who hasn’t excelled at it.
And most likely, if you give that book to an editor, they’ll know more than you do, and they’ll tear it apart more savagely than they normally do.
And if you don’t, the reviews based on the sample will tear the book apart and point out you have no credibility or experience to write such a book.
I’m 66 novels in. I give a lot of advice here. And I don;t consider myself ready for writing this kind of book, even though I’ve had it suggested to me multiple times.
This is NOT a ‘those who can’t, coach’ thing. If you don’t have credibility, no-one will take you seriously.
Before you even start on that kind of book, you need at least 30 novels under your belt which all did better than 3000 in the US paid store.
And you need to be getting upvotes here from the advice you’re giving on these sorts of questions first as well. Just about everything you should be saying in such a book needs to have been put out here first, and validated by others with experience.
The bottom line though is, if you put out such a book, and you don’t have a novel on Amazon less than 2 months old, inside the top 50k paid ranks in the US store, then I will reject that book as the the author having no credibility to write it. If the author has no novels at all, I’ll be telling people to ignore it.
Credibility is everything with a book like that, and you have none just from the question.
So stop. Start writing a novel instead.