After playing college basketball for the Chico State Wildcats in 1972–73,[1] Slacke moved to Australia where he joined the Illawarra Hawks and played in the New South Wales Men's Division 1 basketball competition. The Hawks were preseason favourites for the 1977 Championship behind Slacke and Gordie McLeod.[2]
In 1979, the Hawks were founding members of the Australian NBL. Slacke was part of the inaugural team and averaged a career-best 23.8 points per game in his first season. In seven seasons with the Hawks, he played 143 games and averaged 17.5 points per game.[3] Slacke was one of the NBL's all-time best free throw shooters with an 86 per cent clip for his career.[4] He led the NBL in Free Throw Percentage in 1980 with 87.2% (68/78).[3][5][6]
In January 2018, Slacke was named one of the 12 Greatest Hawks of All Time by the Illawarra Mercury.[7]