This rule is simple: If you make a qualifying hand with or better on top, then your next hand will be “in Fantasyland.”
Fantasyland is treated as a bonus round of OFC. It’s common for the button not to move, and a player is not allowed to quit or get dealt out of the hand during his opponent’s Fantasyland round.
The player in Fantasyland has a big advantage because he or she is dealt all 13 cards at once, instead of the starting five and then one at a time. The player then sets the cards face down in turn, and then waits for his opponents to play their hands according to standard OFC rules.