Don't overfill and don't underfill.
I would put in 4l.
Go and have a cup of tea and watch the news for 30mins.
Dip it, probably will need to add a bit more.
Run the engine for 5mins.
Have another cup of tea and watch the same news stories.
Dip it again and you may need to add a little more or may not.
Then after a few days driving dip it again just to double check
That's my method anyway. I then dip the oil and check all the fluids when I give it a wash. So about once a week/fortnight.
Last time I was at Ford their oil was dead cheap, £13iirc for 5l of motorcraft 5W30.
Also worth getting a new sump plug and washer for about £1.