How do I install the SlimFit 3 LX in rear-facing mode with the vehicle seat belt?

To install in rear-facing mode using the vehicle seat belt, follow the steps provided in section for rear-facing installation with vehicle seat belt. Ensure the vehicle is on level ground, the ball in the level indicator is completely in the blue area, and the car seat does not move more than 1 inch (2.5 cm) at the belt path after installation.