What to look for with a slot receiver?

do you just choose the best attributes for your top 3-5 WRs? Or do you look for specific route running/catching attributes for a slot receiver?

Scheme dependent, but SRR, MRR, and COD are the ones to prioritize if you care about separation vs man coverage.

I usually look for good CIT and route running stats for my slot wr. Since my slot wr is often running one of the better routes on any given passing play I want good route running to take advantage of that. CIT is because I want my slot to have the best chance at catching any quick contested passes I have to throw if my opponent is blitzing.

look at Kupp's stats - 90+ short route running, good AGI, ACC, CTH, ideally his CIT would be higher but you get the deal