To be certain, I recommend:
* Checking your owner's manual: This is the best resource for the precise location of your vehicle's block heater.
* Visually inspecting your engine: Look for a cord exiting the engine block area near the thermostat housing. Be cautious when inspecting around hot engine components.
* Looking at online forums: Searching for "2011 Ford Flex block heater location" on forums like Ford-trucks.com or others might show pictures from other owners.
Because of the potential for slight variations, relying on visual inspection and your owner's manual is the most reliable way to find it.