The terrain blends from this pack were made using a series of gradient masks like the ones in the example below, two terrain textures are manually blended together using the grayscale values, and then each 2D tile was skewed to isometric perspective. You can essentially create a series of interlocking Masks like below, so they are the same size as the height of your desired final tile dimensions (For 256x128 tiles, you need 256x256 masks; for 128x64 tiles, create 128x128 masks, etc.) I'm actually planning to write up a more concise tutorial related to creating autotiles like this!
