The tip of your left foot will point left, or even a little bit backwards.
Because when you prepare, you put all your weight on the left foot, to then move the right foot in the direction you will play the ball.
But that is only if you have enough time.
For the textbook backhand volley you leave the left foot in place, but rotate on the ball of the left foot, and you move the right foot forward.(If you are right-handed, for lefties it's reversed)
Sometimes, when the incoming ball is fast, you don't move your feet at all and just 'block' the opponents ball.