Whenever I get asked about writing I tend to draw a blank so I had go into my notes app and look at the latest one shot I've been working on. The majority of my one shots are pretty short (3k at most) so for those I don't rlly plan or outline. Instead I just have a one sentence logline. So, for example, "Nanami is the only one available to take Megumi to his doctor's appt and Gojo pays him in kisses". A logline is rlly easy for me bcs half the crap I twt are just little fic ideas. It's also a very low pressure thing in comparison to an actual outline. When I come up with one, then I like to think about the tone of the fic. Will it be upbeat? Bittersweet? And the third thing is coming up with the first line. Since it's a one shot it's going to be your only first line so it'll pretty much determine the rest of the fic. Once I have the first sentence, the rest tends to come very easily. If you want to write a one shot and ever want more specific advice you could dm me and I'll have no problem reading it over for you.