Flatters was in an alternating role, as Edgar, in the original
Tricycle Theatre cast of the 2013 play
Bracken Moor. Flatters made his television debut in 2015 as Matt Furnish in the
CBBC sitcom
So Awkward, a role he played for the first two series. In 2017, Flatters began starring as Luke Earlham, the son of Andrew Earlham in the
ITV thriller
Liar. Flatters featured in both series of
Liar. Flatters made his feature film debut as English Allied pilot William Sinclair in the multilingual
World War II film
The Forgotten Battle alongside
Gijs Blom and Susan Radder. It is the second most expensive Dutch film production of all time and had an international release on
Netflix in 2021. That same year, Flatters appeared in the
Channel 4 miniseries
Close to Me. In 2022, Flatters played Tedros in the
Netflix film adaptation of
The School for Good and Evil and Neteyam, Jake and Neytiri's eldest son, in
James Cameron's
Avatar: The Way of Water, the latter of which Flatters auditioned for when he was sixteen. He co-wrote the script for George Jaques' feature film
Black Dog, in which Flatters also starred in. The premiere of the film took place at the
BFI London Film Festival on 14 October 2023, where it was selected for the competition program of First Feature Competition and nominated the
Sutherland Award. In May 2024, Flatters joined the cast of
PBS Masterpiece new adaptation of
The Forsyte Saga as Philip Bosinney. Flatters’ film Black Dog competed at the 2024
Riviera International Film Festival, where he won the Baia Del Silenzio Award for Best Actor and the film won the Baia del Silenzio Redelfi Award. In October 2024, Flatters joined the cast of Benacus Entertainment’s horror 'Your Host' as Harry. On 27 November 2024, Flatters directorial debut feature film 'SHOULDERS' had its world premiere at the Clapham International Film Festival. On 22 August 2025, Flatters's film Your Host had its premiere at FrightFest London. He attended an exclusive screening for
The Forsyte Saga in Soho Hotel London on 2th September 2025. He appeared as Neteyam via a
cameo in the 2025 sequel
Avatar: Fire and Ash. ==Personal life==