He again scored frequently at Hearts, but he became a football outcast in 1950 by signing for Millonarios, of the breakaway Colombian league. Flavell played alongside the legendary Alfredo Di Stefano for Millonarios, but he returned to Scotland the following year to sign for Dundee.
Flavell had five stints as a manager at three different clubs, starting with Ayr United in 1961. He quickly moved to St. Mirren, whom he guided to the 1962 Scottish Cup Final. He briefly returned to Ayr, before having two spells at Albion Rovers. Flavell later became a director of Albion Rovers.