[4] Flack made his karting debut in 2011 in the Bambino Queensland Cup, which he won in that year and in 2012.

[5] Switching to the Energy Course team in 2019, Flack won in the IAME International Final in the Junior ROK category,[6] and also competed in the FIA European Karting European Championship in the OK Junior class in this year.

He moved to R-ace GP for his first full season in Italian F4 in 2022,[3][10] and also competed in the Spa-Francorchamps round of ADAC Formula 4.

[11] Flack made his debut in the GB3 Championship in 2022, driving for Douglas Motorsport alongside Max Esterson and Tommy Smith.

[14] Flack joined Jay Howard Racing Development for the final two rounds of the 2022 Indy Pro 2000 Championship.