Way back in time when I flew control line I use to use large parking lots. I would find one with an edge that was grass. Was not the best arrangement in the world but I made it work. For R/C I would use new industrial complexes that were under construction. They were available on the weekends. The first thing they install is the roadway which of course serves as a runway. Usually there are some hard dirt open areas also.

I would employ someone to hand launch. I learned if I ran directly away from the plane I could get control before it hit the ground.