Make a “sensor” first. It’s basically an empty gameobject with 6 planes added in to make it look like a cube. Then make scripts for the planes to create blocks. For example, the y negative plane would Instantiate a new block 0.5 y lower when clicked. Then put scripts in the original block to teleport the sensor to it’s position when mouseovered. Now when you put your mouse over a block, a sensor appears and if you click on one of the sides a block will appear on the same side. The sensing script should be copied too.