The eastern forehand grip is where the heel pad and index knuckle of your hitting hand are resting on the third bevel of the tennis racket handle. In the video, you can see a shot of me holding the racket with a eastern forehand grip, and you can see my heel pad and index knuckle resting on the third bevel of the tennis racket handle.
A shortcut to finding the tennis eastern forehand grip is to hold the tennis racket with your non-hitting hand and then grip it with your hitting hand like you were trying to shake someone’s hand. If you hit with an eastern grip, your natural contact height will be about waist high, the lowest of the three common forehand grips. Also, if you hit with an eastern grip, it will be easier to flatten out and drive the ball than it would be with either a semi-western or western forehand grip, but the tradeoff is that you will not be able to hit with as much topspin.