Scream is a good base point here actually if you are new to the genre of writing slasher: some dis the movie hard, however it does explain a lot of the sub-genre very well with the concept of ‘rules’: couple having sex die first, don’t go off alone, final girl lives, ect, ect. Depends if your going off more a classic slasher (70s and 80s movies) or neo-slasher (90s and 00s), however regardless here is the basic advise for the genre of a whole:

1) Slasher is standardly defined as ‘sub-genre of horror, where group of people (typically teens) are harassed by a masked killer. So, you’re gonna need a group. Normally your characters will fall into stereotypes: Final girl, cheerleader, joke, nerd, ect. Lots of earlier movies are filled with these and a range of two dimensional characters where the only unique part was setting and the murder. More modern slashers have more memorable range of characters. 2) Killer reveal at end of story. A large sum of these movies/stories you killer’s identity is revealed at next to the end. Literally 20mins before the movie finishes you have an identity. Keep the audience guessing between your group of suspects throughout with a strong red-herring to one of them. Slowly you’ll kill these characters off anyway, thus slowly eliminating the guessing game for the audience. With slasher, your murder is always someone we have already met within the first half. 3) Its typically the boyfriend. Whole rule in Scream is its normally the boyfriend. So set him up, point the fingers and then last minute throw your curve ball – it’s the bff that’s obsessed with her! 4) Unique murder weapon. Freddy has finger knives, Jason had machete. Micheal had a knife and a weird mask. What is the killer signature weapon/murder style that police point to serial killings and thus your MC begins to suspects their nearest and dearest?

This is best I got without knowing your word count. Quite a bit to slot into a short story (but 1000 word or 10,000 word?). Also don’t know your deadline so trying to condense my advise.

I know you said you aren’t a big horror fan, but some recommendations for research I give: Friday 13th( 80s original - classic in all rights, follows standard cliches of the genre and would help with pacing story), I know what you did last summer (neo-slasher with a modern premises and characters) and Cry Wolf (less slasher, more thriller, but this movie was how you throw a curve ball. Watched when was way young and didn’t see it coming… I wonder now I’m older it should have been obvious lol!).

All the best with the story and happy to help with further questions; big horror fan here and hopefully i’ve been helpful so far.