I based my time at the table on when the others are finished. There is always the one that gulps down food and is done in a matter of minutes and then the rest of them including the just sulking ones. I take them down as they finish. That I call it when those that ate are done and simply clear the table. Any complaining and they simply told time is up they should have eaten when they had the chance. It puts a time limit on sulking and stalling this way. Not eating and stalling is not a way to prevent naptime from starting. I do it very casually just clear the plates, wash them up and remove bibs and that is it. They get the hint and some protest but only the first couple of times. I will give a reminder saying time is almost up and time to stop talking and eat faster or something like that - aimed at those that haven't eaten enough.

At the same time I don't believe in keeping the lunch and serving it at snack. It was a one time available thing and that is it. At snack time they get very little anyways as it is to hold them to the next meal not replace the one they missed. There are no seconds on snack ever.