Steps for using the natural method/direct method to make a course, how to use it to teach effectively

Question

If I wanted to write a book or a course using the direct method/natural method, how to do it scientifically? Which methodology to use?

My question focus about the use of linguistics theories to teach, and the method that we could develop from them.

By direct method/natural method, I mean the one used in Lingua Latina per se. (Hans Henning Ørberg)

https://blog.classicsathome.com/2015/02/hans-h-rberg.html

There's also books using what is called "direct method".

For instance: French by the direct method

The Wikipedia's article lists a few advantages, but I can't find an article to explain how to use it as a teacher, and the right methodology.