this is very easy to configure. Set the EMX option USE_RULEBASED_LAYER_CONCEPT to YES and go to your emx_user_config_path or if you don't have one in your installation under configuration. There you will find a folder called templates. In it you will find a part and an assembly called rule_layers. Inside these are defined the slides which are created by EMX when the option is set. Here you can define your layers by you own.