A food product slicer includes a base and a knife mounted for rotation relative to the base. A carriage assembly is mounted to the base for reciprocal movement back and forth past a cutting edge of the knife. The carriage assembly includes a home position forward of the knife and has a tray arm removably mounted to a carriage arm. An adjustable gauge plate is mounted for movement between a closed position that prevents slicing and multiple open positions that permit slicing at respective thicknesses. An interlock arrangement prevents removal of the tray arm from the carriage arm unless the carriage assembly is in the home position and the gauge plate is in the closed position. The interlock arrangement includes a key member rotatably mounted to the tray arm. A key slot may be located on the carriage arm for receiving an end of the key member.