Don't try to as much, stay leant way into the ramp, point your front foot a bit and scoop the fuck out of your back foot the way you would to do a revert on the floor. turn your shoulders before you start to turn to the point where you don't even need to turn them any more while doing the trick.
Edit - unless you mean slides, in which case I assume you can already stall them. I'm not the best at them but it's kind of the same technique as a stall but go at more of an angle that feels comfortable and exaggerate the movement in a bit. You need to push your back foot beyond your bodyweight to make it slide