In this video, bawstansawkscawk99 demonstrates how to throw a slider, as well as the differences between sliders and curveballs. To throw a slider pitch, grip the baseball with your index and middle fingers on top of the baseball in between the two seams and your thumb directly underneath them (on the other side of the baseball and on the middle of the seam.) Throw the ball without flicking your wrist, letting it roll off your index and middle fingers. The ball should dive down and away from the batter. Unlike a curve ball, your fingers will not lie directly on a seam, and you will not flick your wrist at all.