They stormed through the first half.
Within eight minutes, Charlton Gauvain curled the ball over a stranded Northwood goalkeeper from 25 yards.
On 36 minutes, Sam Murray doubled the lead from point blank range.
And as the clock ticked down to end the half, Matt Loaring’s delivery from the right edge of the box evaded everyone to find the net.
There were some warning signs early on in the second half that the game was not over, with GFC goalkeeper Josh Addison called into action.
Then shortly after the hour as Northwood sub Luke Tingey headed home at the far post after the wind aided the flight of an inswinging corner.
It took just two minutes for them to score again, this time a long throw being turned in by Lucas Sinclair.
Another corner created even more problems for GFC on 74 minutes. Stephen Langley found the net from close range after the ball fell in the box.
The Green Lions held on after Northwood wanted a golden chance to make it four when Sinclair blazed over from six yards out late on.
Guernsey FC play Hartley Wintney at Footes Lane on Wednesday at 19:45, before finishing their season away at Raynes Park Vale on Saturday at 15:00.
