With a non-pointed object, it's all about whip and speed at close ranges.
Spin is a non-issue (since you're not trying to stick a point), so you have much greater freedom in how you snap the wrist in the release. Distance is not as critical for a spin throw, so you can be at just about any range. Just remember that the further you are away from a target, the more time it has to react, and the more air resistance will affect to mildly slow your throw.
Closer is better. But a golf-ball sized chunk of rock can make a serious gouge in a wooden target at ten feet or less.