Flint was born in Ontario, Canada and moved to Pennsylvania at an early age. In 1903 he played on a basketball team organized by Pittsburgh Pirates great Honus Wagner. In college, he earned All-American status as basketball player in 1906 and 1907 at the University of Pennsylvania. While at Penn, he played center and served as the captain of the Quakers team that would win an Eastern Intercollegiate championship in 1905-06. He later became the head coach the University of Pittsburgh's Panthers men's basketball team for ten seasons from 1911-12 to 1920-21. While there he compiled an overall record of 105-68 (.607) and was regarded as a "great floor coach" by the local media and was given much credit for building the basketball program from a "bunch of green players". He was noted for his system of "short, snappy passing" and "accurate team play" with excellent foul shooting and "brilliant guards". Highlighting his tenure were city championships and eight winning seasons, in six of which the Panthers won 10-plus games including a 15-2 record in 1915-16. The 1914-15 season saw Pitt in post-season action when the Panthers defeated Penn State at Duquesne Gardens 39-35 to win the sectional title to advance to the state championship in Philadelphia against Swarthmore, which had won the eastern and central championships by defeating Lehigh and Albright. Pitt cruised past Swarthmore 40-26 win to secure the state collegiate championship and finish with a 13-5 record. At Pitt, Flint coached H.C. Carlson, a star in both basketball and football at the university, who himself would go on to coach Pitt's basketball team for 31 seasons and be elected to the Naismith Memorial Basketball Hall of Fame. Following Flint's coaching career, he worked 50 years as a dentist in the Pittsburgh area.