It is important to demonstrate what this sounds like, as well as what it looks like in a mirror. Students can easily recognize a bad flam, or a “clunker,” that results from both sticks hitting the drum simultaneously. I have students exaggerate at first, and insist that they keep the low stick quite low to the drum. Thus, the student is prepared to play another flam, or a single note.
Upon impact, the sticks switch positions: the low stick is now high, and the high stick is now low. Both sticks start moving at the same time, resulting in a flam. I teach the “tin soldier technique.” The main note is your high stick, and the grace note is your low stick.