Position yourself in the corner next to the rock and aim as shown (vertically aligned with the protruding rock to the left, horizontally with the arrow created by the building and treeline below). Move forward until your crosshair is roughly at the second shadowy protruding rock. Hold shift, tap W and jumpthrow (or use a jumpthrow+forward keybind). This lineup is 100% consistent.

On 128-tick, aim slightly lower.