A video on it can be found here: League of Legends Karthus Dominion Bug - YouTube
The way it works, is you must first play a champion with a toggle. Ex: Karthus, Singed, Mundo, etc.
First, begin to capture a point.
Keep your mouse over the point capture.
Activate your toggle.
IMMEDIATELY right click the point again, and it will resume capture.
Activate your toggle again.
IMMEDIATELY right click the point again, and it will resume capture again.
You can now walk away from the point with a giant green beam, and it will continuously re-cap itself.
Only one point will continuously re-cap, but you can collect all green beams, including the stormshield.