Answer: In general, the stacking order of Layers is controlled by the z-index. The higher the z-index, the closer to the top a particular layer will be.
You can create a New Style for each layer and control the z-index that way. Plus you can control many other aspects of each layer using this method. The z-index is located in the Style Builder under the Position Category.
Or you can use the Layers Panel along with the CSS Properties Panel.