This sounds very similar to the process Dean Wesley Smith describes in his book Writing Into the Dark. You could check that out to see a professional and prolific author who ended up taking the approach that you seem to have found naturally.
Here are some suggestions:
Writing into the dark: https://www.amazon.com.au/Writing-into-Dark-without-Outline-ebook/dp/B00XIPANX8
Ten day outline: https://www.amazon.com.au/Ten-Day-Outline-Planning-Novelist-ebook/dp/B07T3H9R55.
Personally I collect a lot of inspirational material such as pictures and articles.
Maybe try this method: writing into the dark. https://www.amazon.com.au/Writing-into-Dark-without-Outline-ebook/dp/B00XIPANX8