Start the class by telling the class that the roles are going to be switched: the teacher will be a student, and students will rotate the teacher role and teach the class something they know how to do for about ten minutes each. It can be something simple, like making a good cup of tea. Take volunteers, and give the student several minutes to prepare. Then give the floor to the student. This not only makes a more student-centered class but also gives students valuable speaking and presentation practice.