You can answer this a million ways, so it's really a matter of opinion and varying strategies. I'll share my general process.
Outline to the outline: Have an idea. Easy. Play it out from the start. If it can't keep your own interest through at least one character/plot arc, it's already going in the trash. If you can make even one small story out of it, then you're doing well. Think about how almost every creative narrative introduces a conflict, and a resolution, early on. Usually this is simply The Call of The Void. Maybe I'm misremembering the term, but basically the first part of the novel is pretty much always the set up for why the rest of the novel exists. If your main character is a detective, then investigating and interesting murder is a good place to start, and you can either resolve it quickly, or use it as the hook. If you like the dynamics so far, then the next step is to pick an endgame. What is the thrilling climax you want in your novel? Don't worry about it making sense yet. What's they moment that you want the reader to feel "this is awesome." Now you have your beginning and your ending, so you can start outlining.
Skeleton: Now you just have to figure out how to get from point A to point B. Luckily, society has long enjoyed the 3-Act story. Even if you split it up later, typically most stories function in threes. Beginning, middle, end. You know you beginning, and you know your ending, so what needs to happen in the middle for it to make sense? This is the meat of your outline, but once again, don't overthink it making sense yet. Once you have all 3 components, start at your beginning and outline each chapter that comes naturally. Once you can't figure out exactly what goes in each chapter, it's okay, you're just linking your beginning middle and end. Just get it done. Then you'll basically have a summarized version of your story, and it's likely the pacing will be awful. That's not a problem. Now you can visually see that in Chapter 7 you have fight sequence, but you only introduced the antagonist in Chapter 6. Now it's super easy to push Chapter 8 back and make sure you plan to have character development between the introduction of the antagonist, and the actual fight.
That's just one example, but it's incredibly flexible. The thesis is that it's way easier to edit an outline until it makes sense than to have 80,000 words and have to fix that. If you mess up on the outline, then you can fix it in a couple minutes. If you mess up on the story, then it could cost you weeks. You can even update the outline while you're writing. Say you introduce a character in Chapter 3, and then you're like "Dang, I really like this character. I wish I wrote them into the story. Now you have the ability to shift your outline around and get it to a point where that makes sense. Outlines aren't any harder than writing. Think of it like baking a cake. You can certainly bake a cake on the fly, it's as easy as pie, but how much easier is it if the exact measuring of all the ingredients is already laid out for you? How much easier is it to have the right ingredients when you decide on the cake you're going to back a week ago as opposed to on the spot?
Essentially, outlining is just telling your story in MUCH less words. When you explain a movie you saw, you don't talk for 90 minutes straight, you just hit on the beats. Jurassic Park is about an theme park that revives dinosaurs for tourism and then the dinosaurs get out and the main characters have to survive and escape, and it ends with a really cool T-Rex sequence. The author's job is now to fill in the blanks. How many chapters is it going to take to show Jurassic Park before things go wrong? How do things go wrong? What happens after things go wrong? How do the main characters survive? What do we want the T-Rex popcorn finale to be like, and how do we get all the characters the right place so the finale pays off? Especially in writing, you'd be surprised that once you're done describing what dinosaurs look like and who soiled their pants, that you're just taking a very long time to build an emotional connection to the story as opposed to just saying what happened like a Family Guy cutaway gag.
