Don't Sit on the Booby Chair
At the front of your class, arrange five chairs and stick a flashcard on the back rest of the chair so the class can clearly see each flashcard. Drill each flashcard until your class is comfortable with the words.
Now choose five students and stand them facing the five chairs, about 2m away. Shout out the word of one of your flashcards. The chair with this word on is now the Booby Chair!