'yass queenslay' is a term popularized by gen z, often used by female teens to express a feeling similar to saying 'you get it, girl!!' or 'she did that!' and is usually used to hype another girl up.
This word/words can be used in a sentence in many occasions. It is used by girls that are amazing and love their friends or the people that they are using it toward.
GIRL, "Guess what!!! I won my cheer contest!!!!!!" OTHER GIRL, "OMG YASSSSS SLAYY QUEEN!!"