Catalogue View of "Unflagged" photos?

I have just finished adding almost 3,500 digitized (scanned) family photos (three generations) into my Lightroom Classic Catalogue.  I have created a comprehensive structure of Collections and begun assigning each photo (flagging them) to its respective Collection.  I DESPERATELY NEED to be able to have a Catalogue view of "Unflagged Photos," so I don't have to keep going through the same ones, using the All Photos view.  Is there a way to set/create a catalogue view (or search criteris) that would select only unassigned photos (thereby reducing the remaining number of pictures available in my grid)?

Thanks,

Gary

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