This method is for anyone who feels stifled by an outline but directionless without one. It's really good for me because I have ADHD, and it's flexible enough that it can handle skipping steps and returning to them later. It's a bastard combination of Randy Ingermanson's Snowflake Method (the starred steps are the ones that are from the Snowflake Method), the Three-Act Structure, and just pantsing it. It sounds super chaotic but it becomes intuitive as you move through the steps. I'm going to use Star Wars Episode IV as an example, as you do.
One-sentence pitch*:
When moisture farmer Luke Skywalker finds himself at the center of a galactic war, he must team up with a wizard, a pair of smugglers, and a princess to destroy an imperial space station before it can do the same to them.
If, like a goblin, this pitch is so shiny you can't resist writing some of your story, go and bang out the first chapter and come back!
Expand the pitch to a five-sentence paragraph.* I don't usually know how the book ends at this point, so I just leave it open:
When moisture farmer Luke Skywalker's aunt and uncle are killed by Imperial forces searching for two droids, he finds himself at the center of a galactic war. He teams up with an old man rumored to be a wizard, and together they learn that the princess leading a rebellion needs their help. They hire two smugglers to take them to her planet, and discover it's been destroyed by a space station armed with a planet-killing weapon. Together, they free the princess from her cell aboard the station and make a narrow escape after a brush with one of the most powerful forces of evil in the galaxy. When they reach the rebel base, they formulate a plan to destroy the space station, but at the last minute, the smugglers decide to take their payment and run.
This is where I usually get excited and write my first chapter, then come back with more ideas for the rest of the book because part three is...
Expand your paragraph to a one-page synopsis by giving each sentence its own paragraph.* This step is amazing because when you're done, your synopsis is ready for eventual queries or submissions! I find it much easier to do in the beginning than at the end, though I usually write a few more chapters before this step:
LUKE SKYWALKER has always dreamed of being a pilot, but he's stuck on his aunt and uncle's moisture farm on a desert planet. When his uncle purchases two droids to help on the farm, one of them goes missing, and in Luke's search for the runaway, he's attacked by nomads in the desert. Luke is rescued by OBI-WAN KENOBI, an old hermit rumored to be a wizard. Obi-Wan tells Luke that he was once a Jedi, just like Luke's father. Hungry for any information about his father, Luke learns that his father was killed by an evil Jedi, a Sith lord named DARTH VADER.
When one of the droids plays a message from a princess captured by Vader and the Empire, Luke realizes that his family is in danger and rushes home. When he finds that his aunt and uncle have been killed, Luke knows that there's no longer anything to keep him on the planet.
Luke and Obi-Wan hire two smugglers, HAN SOLO and CHEWBACCA to take them to the princess' home planet. Once there, they discover it's been destroyed, a space station in its place. The ship is captured by a tractor beam, and towed inside the DEATH STAR.
Luke, Han, and Chewbacca free PRINCSS LEIA from her cell aboard the ship while Obi-Wan deactivated the Death Star's tractor beam. When they think they're about to make their escape, Vader appears to confront Obi-Wan. Luke and the others watch helplessly as Vader kills Obi-Wan, and the crew take off for the rebel base.
When Imperial forces track them to the base, Luke and the others formulate a plan to destroy the space station, but at the last minute, the smugglers decide to take their payment and run. Luke gives up on convincing Han and Chewbacca to help defeat the Empire, and takes off with the other pilots to complete their mission.
All hope is lost when Vader himself enters the dogfight, but Han and Chewbacca appear to save the day. Guided by the voice of Obi-Wan's spirit, Luke successfully destroys the Death Star, securing a victory for the rebels.
We're done with the Snowflake Method now, unless you like to do character summary sheets (which I almost always make, and then leave blank, because I prefer for character to come out as I write). At this point, I outline the first quarter of the book, or Act I of the Three-Act Structure, chapter by chapter. I write approximately 2k word chapters for an 80k novel, totaling 40 chapters, so it'll look like this:
Chapter 1: Exposition
Chapter 2: Things
Chapter 3: Stuff
Chapter 4: Additional things and stuff
Chapter 5: Inciting Incident
Chapter 6: Occurrences
Chapter 7: Further things
Chapter 8: Stuff
Chapter 9: More Occurrences
Chapter 10: Plot Point One
Write some more, until you get bored or run out of outline!
Repeat part 4 with Act II (or just through the midpoint if you decide you Hate It):
Chapter 11: Just
Chapter 12: A
Chapter 13: Bunch
Chapter 14: Of
Chapter 15: Stuff
Chapter 16: Is
Chapter 17: Happening
Chapter 18: In
Chapter 19: Here
Chapter 20: Midpoint
Chapter 21: Oh boy
Chapter 22: Things
Chapter 23: Are
Chapter 24: About to
Chapter 25: Turn
Chapter 26: Grim
Chapter 27: For
Chapter 28: The
Chapter 29: Protagonist
Chapter 30: Plot Point Two
Write some more! Revisit your outline or synopsis whenever you like.
Time to finish the outline.
Chapter 31: Things
Chapter 32: Stuff
Chapter 33: Pre-Climax
Chapter 34: Additional things and stuff
Chapter 35: Some pretty rough stuff
Chapter 36: Occurrences
Chapter 37: Climax somewhere in here
Chapter 38: Stuff
Chapter 39: More Occurrences
Chapter 40: Denouement
Finish your book!