Slider Aim is the player’s ability to aim fast and uncomfortable sliders. But what exactly are “uncomfortable” sliders? Well, if you take at look at some examples, you’ll notice that large, sharp changes in angle are harder than small, smooth changes in angle. Sometimes those smooth changes in angle can still be difficult however.
You can think of Slider Aim as a slightly simpler version of Flow Aim as you don’t have to worry about slider velocity slowing up or speed down (which is unrankable).
Source: https://www.youtube.com/watch?v=e75DXwOiZ40
Source: https://www.youtube.com/watch?v=RYLD1CJSBvU