I used a large saw to slice the stone base into a thin veneer and after sanding the bottom edge, I glued it to a wooden disc that I had in my spares box. The disc is 58mm diameter and 6mm thick.
I built up the flag stone base with some Milliput and then added groundwork from DAS modelling clay which was further textured with sieved stones and sand applied over PVA glue.
These last two images show the models ready for undercoating. You can also see the miscast on the little finger of the shield hand.
I'll be undercoating later today and will post images and progress later.