So far I find this a fun fight personally, but I only see Slayers so often on ranked. If people are having trouble I find that f.s, f.s(whiff)>5HS, 5HS are great pokes against Slayer's Dandy steps. Also on knockdown, he has very few answers to 6K meaty. Hope this helps a little.
Edit:
Some extra things I forgot to add and that I just learned. 2S is great for Slayer dash mixups as well as just a generally a good move for this match up. It'll hit behind you if he tries to go there, and it can stuff some of his more long start-up moves.
In my last match with a Slayer, I was having some success with 5HS, both on his jump in cross ups and some of his dash cross/mixups. Don't know the actual validity to it's use, but if you throw it out there once in a while I'm sure it'll at least give you some surprise big damage combos.
To add to the 6K meaty option, the answers I've seen to it so far has been wake up Dandy Step, if you condition him to always Dandy Step on wake up you can catch him with f.S and 5HS.