People don't really know how to use Trample well. You can launch in a LOT of places with it. Nexus definitely has the most instances.
Really though, you just release your charged trample as you're coming around the corner into their base and up the ramp. If you don't turn, you usually end up on top of/over turrets and can have your way with the base. If you turn slightly, you tip the tiny incline in the side of the tube and launch over, right out the other side of their base if you happen to line up right.
More of the skill is knowing how to hold your charge and release it at the opportune moment. You don't have to be moving to charge. You can charge your trample while you're running into the wall around the corner, or just walking forward with the keys but using the mouse to go in a circle instead.