we recently had a huge ant problem, the only thing that worked was two mixtures, one was borax and very finely grated parm cheese the other was borax, icing sugar and cornflour, it took weeks, yes weeks to kill the entire nest but it did work, it was sooooo frustrating, we had them everywhere, throughout my pantry (nothing kept the away) bathroom, shower etc...
we were told not to spray the nest as doing that just kills those in it which therefore means the remaining ants start new nests

ETA these recipe were from shannon lush