The phrase "meeting slot" is correct and usable in written English. You can use it to refer to a scheduled meeting time, or a time slot that has been set aside for a meeting or appointment. For example, "I have a meeting slot at 10:00 AM tomorrow.".
A Casino Party (also known as a Casino Night or a Monte Carlo Night) is an event where you experience the fun and excitement of playing in a real casino, but instead of you and your guests going to a casino to play, the 'casino' is brought to you!