Once the sides of the plinth had been sanded and the groundwork detailed I added some small stones and fine sand to the centre of the base area. In this photo you can see how I have carved the rock or stone face with a scalpel and how the DAS groundwork now matches, seamlessly with the building blocks. You will also notice how I have not yet attached Hellboy's right arm, as this would have made sanding the sides difficult.
These photos do not show how fine, ready-mixed filler was used to fill the joins between the building bricks. I added some filler and white glue to the joins and when dry the joins were sanded - this took about three attempts before the fine joins were hidden.