Slater made his professional debut for Kilmarnock on 29 December 2012, in an away match against Motherwell coming on as a substitute in a 2-2 draw [REF].
In the 2013-14 season, after a substitute appearance on the opening day of the season, Slater began to establish himself in the first-team during the Autumn of 2013, and in February 2014, he was named as the SPFL Young Player of the Month for January [REF].