On his way to the final, he defeated several of the top players in the World Darts Federation ranking, including Nick Kenny, Neil Duff, Richard Veenstra and Chris Landman.

He managed to qualify for the PDC World Youth Championship 2022, in the group stage, he remained unbeaten and would eventually reach the quarter-finals, in which he lost 4–6 with Josh Rock.

[12] In 2023, he took part in the 2023 UK Open where he defeated Maik Kuivenhoven, Shaun Wilkinson, Robbie Knops, before losing to Joe Cullen of England by 7–10 in legs.

[13][14] Slevin made his PDC European Tour debut in the 2023 Austrian Darts Open where he lost to John Henderson of Scotland by 4–6 in legs.

However, ninth seed Danny Noppert withdrew prior to the tournament due to the imminent birth of his second child and Slevin came directly into the draw to replace him.