Flionis began playing basketball with the junior youth teams of Aris Thessaloniki.

On June 30, 2018, Aris announced that they had rescinded their contract extension offer towards Flionis.

However, four days later, on July 3, the team and the player officially agreed on a new two-year deal.

In 23 league games, he averaged 6 points, 3.6 rebounds, 1.6 assists and 1 steal, playing around 24 minutes per contest.

[4] During the 2022–2023 season, in 19 league games, he averaged 7.1 points, 3.6 rebounds, 2.9 assists and 1 steal, playing around 22 minutes per contest.