I have applied lots of materials for my class such as commercially made movie clips, photos, text etc. Among them, my students like the movie clips I made for the class starring my real students. Bt it requires so much time and energy for the teacher to come up with idea and make up the movie clips by themselves. Even more, despite the teachers' effort, the very movie clips that attracted the learners attention at the beginning might lose their fresh attraction over time and the learners could get bored easily. Teachers should train themselves handling technology for making up movie clips fast and effectively. Furthermore, as there are always some students who don't finish their homework at time, teachers may have some learners who miss the required assignment of previewing the class online. Teachers should set rules to motivate and encourage them to work actively.

Design online contents for previewing the main class is a great challenge for the language teachers not skillful for dealing with computer technology. Not surprisingly, the quality and credibility of the clips the teachers make can never be as good as those made by professional movie makers or programmers. And as this method is still new and unfamiliar to teachers and learners, it make take some more time settling in our actual school settings in Korea. Evaluating and incooperating into regular curriculum are another difficult problems to solve. And it may be a great burden for the learners to have all the subjects other than language through flipped class.