I created this stylized lava texture in Substance Designer 2018.2.2.
To roughly summarize my process, I used 4 different Polygon 2 nodes. 3 of the Polygon nodes are plugged into a Slope Blur Grayscale along with either a Clouds 2 or Fluid node to roughly get the shape of rocks. The 4th Polygon is plugged into a Splatter node, which is then plugged into a Bevel node and blended with one of the other rocks. The 3 rocks are then plugged into a Tile Sampler, which was used as the base to create the rest of the texture. In these textures, I have set up slider bar controls for the size of the rocks and for the opacity of the lava, so the material can be easily altered and adapted.
The texture maps for this texture include: