What I did for the king is dead: i did not write without knowing / or having a good idea how I would want to end the story. Once you know your end and your beginning, all that's left is really bridging the two things.

So you could break it down by having a bunch of "key scenes" you'd like to hit in your story, then start arranging them by how easy each one is to achieve (and thus creates a plot arc for you to follow).

Once I have a general guideline of the storyboard, I kind of just wing it, and go gung ho on my first draft. Then used the feedback I got from wba to refine and reforged the second draft.

Then voila done.

 

My thoughts on it are here, somewhat:
https://forums.darklordpotter.net/threads/writing-resources-thread.38750/#post-1120928