Slayers either skulk around the underdark looking for illithids or recover in the larger cities that are close to entrances to the underdark.
Attitude against slayers
Most people who reside in the underdark revere slayers, being thankful and helpful to them. Which only makes sense, as illithids tend to be unfriendly right up until they suck your brains out of your nose and ears. Most non-adventurer surface dwellers have never heard of illithids, and hence also have no knowledge of slayers.
There are no organised slayer guilds, but that is not to say they dont band together when going on hunts. There are simply not enough slayers in Polaqu to make a guild a profitable business.