The base was a simply done thing really.
A slab of 12mm MDF board which was then landscaped so to speak with epoxy putty and the rubber tracks from the kit were pushed into it at the appropriate points for marking.
When cured abnd rubber tracks removed, grass matting usually used in model railway senic stuff was glued on to form the main grassy base.
Two strips for the tank tread tearup were left clear.