The Flipped Classroom pedagogy has been developed for being responsive, student-centered and promoting self-directed learning. Three years ago, we started an international research project aimed at understanding how the FC can be implemented by secondary school math teachers through the use of a MOOC (Massive Open Online Course) developed at the Polytechnic of Milan. In particular, we focus on the teachers' use of MOOC videos. A variety of scenarios emerged from our direct classroom observations and work-in-team with the teachers. In this paper we propose a sketch of such a variety of FC implementations.