You don't have to own land to get away from it all. One might even say that not owning land is a prerequisite for true freedom. Squatting in the wild does pose some challenges, though.
I know several people who have lived for years and years in assorted tipis og tarp sheds in the forest and never been bothered by anybody. Half of them have been young, outdoorsy students and/or artist types, the other half have done way too much drugs.
The rules, most places, say you can not camp more than three nights in one spot. So the challenge is either moving around like a real nomad, or staying out of sight.
Most squatting rules were originally implemented to keep poor people from saving money, but now that most of us have been brainwashed to believe we need so many amenities land owners and public areas are no longer in danger of being overrun by the maddening crowds.
Siting: Maybe settling down right next to a road or a lake will work for you, but very likely some inquisitive fellow will start asking all the wrong questions. If you are visible from a road or from a lake, you will be very, very vulnerable.
An ideal place would be a south-facing slope quite close to a river and quite far from trails. There are no really dangerous large predators in my area, so the main animal to worry about here is the mosquito.
Housing: Building a small and at least mildly professional looking shed has it's advantages, as most casual walkers that happen to stumble across it will presume it's supposed to be there. On the other hand, if some ranger or land owner makes a fuss you will have a hard time convincing them you've only been there for a couple of days. Also, transporting building materials will get you noticed in the end.
Making a log cabin with trees from the site opens a whole can of legal worms. Only recommended if the chance of being discovered is very, very low.
There are various tipis and large tents on the market. These have the distinct advantage of being portable, and with some ingenuity they can be insulated in winter. The site simplydifferently.org has a wealth of information on these kinds of dwellings.
In my climate one of the best alternatives for stealth living might be a sod-covered igloo. One example is mentioned in an old article in Mother Earth news, another example can be found in that treasure chest of hippie building lore, Lloyd Kahn's Shelter. These are almost invisible, well insulated and don't require transport of loads of building materials.
Heat: A sheet iron wood stove combines efficiency with at least some degree of mobility. Again, for legal reasons, it's probably a good idea to stick to fallen trees, debris from clear cut areas in the vicinity and so forth, rather than chopping down the trees around the site. For making food, camp stoves honestly become sort of fiddly and irritating in the long run. Maybe a rocket stove would be a good idea.
Escape: A guerilla homesteder would be wise in planning her escape well in advance. Strategies are storage spaces kept at a good distance from the dwelling and (this sounds insane in this context) also a "summer home", some simple structure to retreat to in case one's place has been overtaken by the land owner's minions or public park zombies.
The fanzine Dwelling Portably has over the years presented lots of tips on permanent camping and storage ideas for squatters. The issues have now been collected and reissued, heartily recommended reading.
Health: One reason for the "three night rule" that actually makes sense, is that campers can end up making a horrible mess. One of the first things to consider when settling down on the wrong side of law is what to do with one's own feces. I know camping guides traditionally bray on and on about digging a deep hole and covering it all with a stone but you're not going to do this day after day. And digging a hole to make a latrine certainly isn't a good idea in cold, wet climates as rainwater will seep into it and it will all end up smelling horribly.
One option is shitting straight on the ground different places in a large area. Unless you're on antibiotics, you're shit isn't all that much more hideous than any other animal's shit, and they're not digging any holes or covering it up with stones. Your excrements will disappear quickly and feed the earth.
Camouflage: A guy I know built a small shed in the woods where he stayed some years while on heroin. It was so well camouflaged that one day he woke up and found a family sitting around with hot dogs at his camp fire site, ten meters (thirty feet) from where he was sleeping, completely oblivious to the fact that they were right next to an inhabited structure. He was so worried of scaring them that he stayed inside all day, pissing in an old water bottle.
Avoiding straight lines and crazy colors on the structure goes a long way in camouflage, as does sod roof coverings in case one is paranoid about those helicopters. In an area with snow, though, one will leave tracks. That stuff in old adventure books about dragging a large branch while skiing to cover over one's tracks does work, but man, it's a pain.
Keeping the area tidy is perhaps the best way to avoid trouble. A place with lots of junk registers much easier, and in a much more unfortunate way, than just a pleasant little home.
What you can't do: You can't wash your clothes unless you really make an insane effort. Unless you're living as a gatherer-hunter you're going to go to town anyway. So do your laundry at laundromats or a friends'. Also, you need some "real" address. Most governments do not accept post box addresses or even employers' addresses, precisely to avoid people going off into the wild like you.
Quality of life: Woodland squatting is rough stuff, even by my standards. But it will force a strict limit on the number of possessions, which most describe as very liberating.
Also, what is "rough"? I live in a cabin without running water or mains electricity, and often feel I am the one who's taken the easy way out. If I didn't have a mortage, things would be even easier. But it would be hard to keep animals.
The ones I know who have done this have all chosen sites that were very close to public transport, but still completely out of view. Typically the areas close to railway tracks or roads are not considered very interesting by land owners or hikers or skiers or bicyclists or whatever. Weekend warriors will start off from defined nodes like bus/ train stations or parking lots, and fan outwards from there. The areas close by that are in the "shade" of these triangles are pretty safe, though perhaps not as idyllic as one would like.