Beginner needs help - Can someone give ideas of places, preferably free, to practice??

I’m a beginner wanting to learn/ practice spins, backward skating etc.
Been looking at tennis courts but they always seem to be in use or someone eventually wants to use the courts. Parking lots can be land mines with pot holes and trash. Where are the best types of places with relatively flat ground or smooth concrete to get my skate on and practice for free. The rink is the only place I know but again looking for free. Any suggestions? I’m in So Cal.