I am trying to create a great cube with the size of (5302 x 2908 x 2700) m. This cube consists of three materials with different site. The first top material is located from depth of 0 to 1620 m, the second middle material is located from depth of 1825 m, and the third bottom material is located in the remain space of the cube. Here I attach the configuration that I described before. As we can see in the figure, the 2nd layer is constrained by the two green horizons. To define the material of 2nd layer, I intend to fill the space between the two horizons. Can anyone please tell me how to and such as solid part for the second layer? Or maybe there is another better way to determine material for second layer?