This part snaps in place on the lower frame support at the front of the car, behind the front bumper and under cover. They're listed in the service manual as a "front air spoiler", but these don't generate any downforce. It's placed upside down under the car.
The purpose of this part is to direct road debris away from exhaust and engine components under the car, and to alleviate some wind drag. The flat side with mounting clip holes faces the front of the car.