From an area off-screen. You can predict its presence by a sound that precedes it.

[Spock becomes quite engrossed with the game, letting silence settle between them. But his curious nature can only hold out so long.]

I am curious, have you made a habit of holding others by phaser-point? Or has the situation changed for you?
[Congratulations Leia, you have just been exposed to Spock's abhorrent sense of humour.]