How does the game of Uno stacking work, and what are the rules for stacking cards in Uno?

In Uno, stacking allows a player to play a 2 or 4 card on top of another 2 or 4 card, making the next player draw more cards. The rules for stacking cards in Uno are that the next player must draw the total number of cards from the stack, and they cannot play a card to avoid drawing.