You typically boondock on Public land. I use the app "US Public Lands". It's free, and will help you understand where these public lands are. There are typical stay limits on public lands. They don't want people living on public lands.
If you get caught on someone's private land it can result in legal issues. Especially in rural areas, land owners know their neighbors, vehicles, etc. If they see someone "squatting" on a neighbor's unoccupied land, they will call the sheriff. Excuses like there was no fence or signs don't work. Ask me how I know.