In 1998, he began filming a musical portrait of the Boston-based rock band The Upper Crust. Developments within the band led Flender to continue shooting on and off for the next five years. The resulting documentary, "Let Them Eat Rock", played film festivals in 2005 and 2006 to mostly positive notices. Following the 2010 Tonight Show conflict, Flender joined Conan O'Brien (whom he knew since their days at Harvard) on the road, as part of the Legally Prohibited from Being Funny on Television Tour, and filmed the ongoings behind-the-scenes, onstage and between shows. The documentary, titled "Conan O'Brien Can't Stop", was released in select theatres on June 24, 2011, which Roger Ebert featured on his list of best documentaries of 2011.