The pads on the bottom of the Lateral Force Accessory (2D-FP) are intended to be effective at gripping most surfaces. However, if leveling the platform is important for you investigation, there are 3/8″- 16 threaded holes that can accept feet.
You can source feet with threaded bolts attached most anywhere you purchase hardware. We suggest a foot with a large diameter and a grippy surfaces such as this one: https://www.globalindustrial.com/p/vibration-shock-absorption-mount-threaded-stud-200-inch-dia-75-inch-h-3-8-16-thread
The same threaded holes can be used to secure your 2-Axis Force Plate to a surface using a 3/8″ – 16 bolt.