The star, 24, who won an army of fans for his role as Connell in the raunchy TV adaptation of Normal People, is sitting for Sky Arts Portrait Artist of the Year.
The show pits amateur and professional artists against each other as they hope to wow the judges with their skills.
A total of 24 actors, musicians, writers and TV personalities pose for portraits.
They include actor James Nesbitt, broadcaster Sir Trevor McDonald, First Dates star Fred Sirieix, TV presenter Melanie Sykes, musician Ray BLK, TV presenter Katie Piper, TV judge Robert Rinder and actress Jane Horrocks.
Nine artists compete in each heat, and go on to paint Booker-prize winning author Bernardine Evaristo in the semi-final.
The winner receives a £10,000 commission to paint the director of the Birmingham Royal Ballet, Carlos Acosta, with the portrait to be exhibited at Birmingham Museum and Art Gallery.
Programme-makers said the series, hosted by Stephen Mangan, was recorded with strict safety protocols at Battersea Arts Centre in London.