This is an intentionally humourous play on the phrase Religion of Peace, in regards to Islam. Because adherents of Islam engage in dismemberment of enemies and rivals, spectators have coined the phrase "Religion of Pieces".
A reference to the movie Office Space. Fifteen pieces of flair refers to doing the bare minimum amount of work required for any task. Barely meeting a standard, usually intentionally.
Courtney knew she was about to graduate and that her presentation wouldn’t affect her grades, so she went all 15 pieces of flair just to meet the requirement.
A saying used when someone you hate dies. Opposite of "Rest in Peace", where you would rather think of this person rotting/decaying into pieces than resting in peace.