The Noise Generator dialog allows you to quickly create flat tiles from a randomly generated noise texture (using the OpenSimplex noise function). It can be accessed from the Voxel Editor toolbar when editing a tile. To use the tool, select a base color from the color picker button, then click the “Generate” button until a desired pattern is achieved.

Once you are happy with the generated texture, click the OK button to apply it to the bottom voxel layer of the current model frame.