T's a sad state of affairs that flopping in the NBA has gotten so prevalent that there actually has to be a button for this in NBA 2k19 with , however we are. We can't blame 2K, that's for certain, as they are merely trying to make their game as authentic as possible. It is just a little sad that is all.
What flopping is for those that are unaware, is when a defending player drops over dramatically to attempt to deceive the referees into believing that an offensive player that's driving toward the basket billed through them. When done properly, you can draw a filthy and add into an opposing player's personal foul count, and the overall team foul count.
To flop double tap O/B/A as the opponent is driving into you. If done correctly (try to time it out as somebody is attempting to drive/attack the basket), then you are going to fall over and the referee will call a offensive foul on the opponent.