Postflop AA is just a hand, and it should be played like any other hand. Whichever your holding you need to classify your hand as either value, showdown value or bluff. AA is usually not a bluff, because you always have at least an overpair, but it can be either value or showdown value depending on the board texture and previous action.
You never want to slowplay a vulnerable hand, and an overpair is extremely vulnerable, so that is pretty much never a good candidate for a slowplay. A full house or quads might be though, because its almost impossible to draw out on, and with AA you also block many of your opponents strong holdings. So on a board like A44 and even more AA4 it can be reasonable to slowplay AA and allow your opponents a chance to catch up a bit.
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