There was a lot of trial & error involved. My plan was to select a bunch of fanfic ideas sitting in my notes & work them into story outlines. How much of an outline I'd get would vary of course. A multi-chapter longfic or a oneshot with a lot going on would get a bulletpoint summary of the plot, while a shorter/simpler oneshot might get a very very rough 'insert cool stuff happening here later' draft.
Because I couldn't be sure which ideas would work out, I didn't select a week's worth of idea's in advance. There were a couple that were promising because I'd worked on them enough that they had taken up their own section in the notes app because they needed multiple pages to cover the planning, & a few that had individual notes pages because they'd come from Tumblr posts that had gone into some detail on suggestions for the prompt, & then there was a page of miscellaneous ideas. I just created a new section in my notes, copied a bunch of ideas pages over, then culled anything that was too vague (there were a bunch of 'ideas' that were basically intriguing Ao3 tags I'd found) or was more an idea for something that'd be cool to include within a larger fic. And that was my pool of ideas to work through.
( Day by day )
So I have a bunch of stuff ready to be worked on, which should hopefully encourage me to get writing them, simply by having an outline ready, so there's less initial work to do.
I might actually do this again. There are a couple of ideas still left in my notes. Plus my Tumblr has a 'writing ideas' tag full of posts where people suggested interesting ideas, that I could go through & decide if they'll actually work. I do have things to do this week though, so it'll have to wait.