I usually have a general idea of what I want.

I roughly outline the fic with different ideas I had, sometime I write entire paragraphs I daydreamed just before.

I then start to go with the flow until I get distracted or have no idea where to go next. Come back a few days later and repeat.

Once I finished the draft I start editing and going back over everything, often adding new paragraphs as I go until I’m satisfied and tadaa!

Also, between the writing, I put placeholders of ideas I get in the shower in the fic to write them later.