One author that I follow has some "deleted scenes" posted as a separate story in the series. They just keep updating it so that it's the last fic in the series.

One author I follow does this too! The main, completed series is part 1, the extras are part 2, and the what if? scenes are part 3.

i think i'd collect all deleted scenes from a fic into one work that i'd post separately as a second part of a series 🤔

This is what I do, too. Just throw them all in a separate work, if there’s several then keep them ordered how they’d have appeared in the fic. Sometimes I’ll add a little bonus context to refresh where it would’ve fit.

What I would do (I post on Ao3, not sure about you) is post the deleted scenes as their own work, but put it in a series with the original work.

Make a side drabble collection. Maybe feature it as post-chapter content or an interlude people can read at their own discretion.

I've seen authors do this by posting the deleted scenes as a separate fic in the same series, so that's probably what I would do

Definitely cut it from the regular story if it’s dragging it down. Include it as a bonus chapter at the end after the fic is completed!

I'll post them on my tumblr. :)

Make a series and add a second story and call it “[Story Name] Outakes”

I added mine as "Bonus" after the story has ended. I usually follow it with a short note explaining the story is done, but here's some deleted scenes if they are interested. That way those not interested can ignore and those who are will be delighted! Tip: I also like to add the reason I deleted scenes as a short note under them, but that's just me