When setting up custom base maps how do I set reference services/layers?

dewright_ca

I have and maintain several internal base maps we use across apps and we would to setup the services like we see in ESRI hosted services with the main BaseMap layer, but with one or more Reference layers/services. But I am not able to find where in Portal or ArcGIS Online I can set a item in my Contents to be a Reference layer.

Suggestions?

dewright_ca

No. I am working in 10.3.1 and setting up my own basemaps using build caches, and wanting to add my reference layers similar to how ESRI does with the Light Gray Canvas basemaps.