The most evident way to justly obtain property is through voluntary exchange. In this case you would know you owned it because you voluntarily exchanged with the previous owner is some sort of agreement where the ownership of the land was transferred to you.
And, if I say I own your land? How do you prove it is yours? Let's say, for example, you have 20 acres, and I claim that 10 of those are mine because I have been camping there for ten days without your knowledge, and I claim "squatter's rights". How do you prove it is yours, and to whom do you need to prove it?
BTW, I am very heavily armed.
You stated this before, but like I said merely purchasing property in a region which other people (government) claim to have the authority over is not a form of consent. You may be aware of the those claiming authority, but this is not consent unless they own the land you live on.
Where is the legitimacy for this "proper and just authority" that government claims over large regions of the world? I think this is the main focus. If we can find where people calling themselves government obtained their "authority" over these regions, then the legitimacy of governmental authority will be true.
For the United States, it is in the Constitution. We, the people of the United States of America....do ordain and establish [the] Constitution..." We, the people, through our ancestors, established the means and manner of who governs us, how, and how they are limited in what they do. We, the people, reassert this authority over the government every other year as well as through our state governments (which also have people-established constitutions) having control over the Constitution.
In other words, the government is not "people claiming to have authority", it is actually people who have authority, and we gave it to them. If we don't like it, we have many redress procedures to follow.
The only way to be one's own country is to find land that no one claims authority over, and colonize it yourself. Now, you and you alone can claim to be the government. Otherwise, wherever you live there is an established and recognized authority.