The son of Peter and Carole, Slater was born in the New South Wales rural city Wagga Wagga after his parents and two elder siblings (Julian and Tracey) had emigrated from the north-eastern coast of England in 1966. They originally migrated to Launceston, Australia by boat, after deciding against moving to Canada. In Launceston, Slater's father taught agriculture and science at high school, as he had done since graduating from college. After three years in Launceston, the Slaters moved to Wagga Wagga, and Peter became a lecturer in agriculture at what is now known as the Charles Sturt University. Slater lived in Wagga Wagga for his entire childhood, eventually leaving with only fond memories. He later wrote: "Wagga Wagga was a great place to grow up, for many reasons. It was a good size — it had a population of around 50,000 when we moved there — and it was in the country, with a great Australian climate. My family was always involved in sport, so from an early age it just seemed natural for me to play any game that was on offer. "