I really need to modify the dimensions of the substrate, but can not do it. I find articles on the Internet to design substrates with three dimensions. For example: "Substrate Dimensions: 26x45x1 mm". But when I click EM Simulation Setup, and then in substrate, I create a new substrate. For example, the default is Alumina, then click on the layer, and then I have just the "Thickness" option. How can I set a substrate in three dimensions as well?