He is the Artistic Director of Belvoir, a theatre company in Sydney's Surry Hills.
Flack studied acting at the Western Australian Academy of Performing Arts.
[3][4] Two productions Flack directed for Belvoir have won Best Play at the Helpmann Awards, Angels in America [5] in 2014 and The Glass Menagerie[6] in 2015.
He was nominated for a Helpmann Award for Best Direction of a Play in 2016 for Belvoir's production of Ivanov.
[7] He cowrote The Jungle and the Sea with S. Shakthidharan, which won the 2024 Victorian Premier's Prize for Drama.