Rolling start, clipped in, apply your knowledge of the segment to know when to really go full gas (any uphill bits) and where you can ease off a tiny touch if need be. Empty the tank with a 20 - 30 second gallop to the end. That should, as others have already said, find 7 seconds in like for like conditions. If there is a slight tailwind, so much the better.
7 seconds in 3 minutes can be as simple as course knowledge.