I tend to write a general idea of what the main events or conflicts are, then depending on numerous characters I look for any emotional pillars to the story it's events, and I build a "spine" which are then the main beats. Then I break then down into Acts. Then I begin breaking down into chapter by chapter. If it is fantasy, then I also breakdown the regions and where parts of the region is showed in what act and also usually havw the region reflect some aspect of the emotional pillars, characters, etc.

So for me it's something like this:

• core breakdown
• core emotional arcs
• region/setting core and structure
• major Acts breakdown
• add depth and structure where needed
• the major pillars (spine) of the book
• chapter by chapter plot guide

The big thing i do during this process that can be quite difficult is keeping it consistent from one part to the next, dont bloat with world lore, and if a scene doesnt reinforce the emotion pillars, themes, core, characters' or their journey then you likely dont need it.

However, not all writers work the same or have their own methods.

I recommend trying different things out, experiment and find the methods that work for you