I’m always selective about my choice of rocks. I try to use the ones that have been disturbed. I leave the ones that have been there a long time because there are millions of creatures (bugs, ants, spiders, etc..) have their homes under the rock.
When leaving I place the ones I did use back and try to leave the area cleaner than I got there.
I survey the ground with my eyes before parking and pick the best spot that the truck will be level without using rocks, wood or... After you do it for years it becomes easier. I also have two level gauges right inside the cab wall that I can see in the drivers seat. A glance over my shoulder will tell me when to stop and how much bubble out but within the refrigerator limits.