To perform a Flat Spin simply drive up any ramp and when the car is almost at the very top of the ramp tap the E-Brake button and steer hard left or right. The car will then spin while in the air, and the game will track the rotation you achieve.
Some cars are harder to spin than others depending on their traction, boost type, size, and weight. Stunt cars are the easiest simply because they are made for flat spinning. Most of them are lighter and have tires with less grip on the road, which also makes them drift a lot better than a car with a different boost type. Speed Boost cars are usually much harder to spin because their tires have much more grip on the road. Aggression Boost vehicles are harder to spin usually because of their size, and/or weight.
During online multiplayer games the session keeps track of the largest rotation by each player in the game, and beating the highest score causes an alert to all players.
Players may earn an Achievement by performing a full 360 degree Flat Spin in any car.