I started writing fan fiction for Star Trek role playing sites, so I do my novels in the same method. When I write it is usually in the short story style, but unlike fan fiction, there isn’t any one to collaborate with. It’s like doing really long blog posts and stringing them together to make a book. It helps when my days are hectic. I start a chapter and if I cannot finish it I jot the thought down and close the document. The next day, my brain may not be in the same place, so I probably will open up a different document, start different chapter.
This makes for problems of continuity. Sometimes I forget where the thoughts were going, sometimes I lose the original direction of the entire piece. And sometimes it makes the chapter better.
So, when I begin to put things together, there can be time gaps, character confusions and setting changes that would not happen if a story were told start to finish.
I find that I spend a great deal of time is spent putting the bits and pieces in the correct order. Then I have to read and re-read, because things get moved around like a slide puzzle.
I have found that my word processor does an automatic table of contents, which is grandly helpful. It makes blending the “a” portion of the story with the “b” portion so much easier.
And like fan fiction, more on both of these subjects later.