If the edges or sides have some type of frame or surrounding material, use threaded rod and sq plastic blocks to hold them down. From lawn equip to industrial electric carts and automobiles, EVERY battery should stay in position so as not to contribute to causing a fire by arcing.
In the most horrific crashes the battery can still cause a fire but in general the battery should be secure.
Even on stationary equipment like generators or water pumps, the battery should be secure or you will find a hole worn through the side when it vibrates against something hour after hour. JMO