It was goalless for a long time at Old Trafford, but considering that Manchester United had a total of 3-0 from the first meeting, the final place felt clear for a long time.
It also became definitive when the home team received a dividend and broke the deadlock.
Wout Weghorst was substituted after 63 minutes for Anthony Martial, who slotted home the 1–0 ball low from close range ten minutes later.
Then the air went out of Nottingham.
The extension came just three minutes later when Fred kneeled to make it 2-0 in an empty net after Marcus Rashford's delicious delivery.
Swedish Anthony Elanga was not selected and Victor Nilsson Lindelöf played the last ten.
There will be an interesting Swedish meeting in the final where Manchester United meet Alexander Isak's Newcastle.
The match will be played at Wembley on February 26.