He kept his first clean-sheet on 12 December 1959 at the Eastville Stadium, Bristol Rovers were the side that were unable to break down the Reds defence as Liverpool won 2–0.
Slater was small for a goalkeeper standing at just 5 ft 8 in (1.73 m) and was nicknamed "Shorty" but he was immediately put into the Liverpool goal upon his arrival in 1959 after a disastrous start to the season the No.1 shirt was handed to Doug Rudman, but when Bill Shankly arrived Bert got his place back and went on to clock-up 30 appearances in all competitions.
Shankly rallied his troops and also brought in Ron Yeats and Ian St John to strengthen his side, it worked, Liverpool won the division by 8 points and were promoted to the top tier of English football after an 8-year break, Slater played his part by appearing 29 times, but he now had serious competition as Shankly had signed James Furnell from Burnley.
Bert moved to Dundee in July 1962, which meant that he was sold by Bill Shankly and signed by brother Bob.
If they were by the 27th minute they got their man, Slater took a boot to the head which opened up, he was replaced by Andy Penman, an inside-forward, there were no subs back then.