These Protolene SCI-FI vehicles in 15mm from Critical Mass Games have mostly been based on metal disks with the exception of the Fenris model which is on plasti-card.
I then used the Windsor and Newton Texture gel mixed with fine sand for additional grit factor. The gel makes it very easy to build up to the edges of those large toe platforms under the small vehicles.
The legs on the bigger model are tricky and require some careful placement. I also wanted to keep the base size down so I angled in the toes on one side to keep it on a narrow plasticard base. It was a case of using some blu-tac first to get a position before marking and then gluing the feet on the base.