I think the only chance you have of staying on the right side of the law (and of doing this safely over the long term) is to do it partially.
This crops up from time to time and recently a lot of information including the more obvious pros/cons was offered in a
couple of
threads
Without permission sooner or later you're going to fall foul of the law, no matter how remote a place you think you are in, so it makes sense to work within those boundaries for a number of reasons.
You can choose to "live long, and prosper" and still not be a 9-5 stereotype, but if you try and do it alone, 24/7, you will be operating outside of societies rules and regulations and, sooner or later, this will trip you up.
The recommendation for a large knife makes sense from a practical perspective but it is also one of the fastest ways of getting into trouble I can think of, so you need to be careful of where it is, how it is stored, carried and used and so on.
Years ago I played at this for a couple of months on the west coast of Scotland. Me and a mate wanted to do a 'full-on' skills test and I have to say that the easiest (read "least difficult") environment was coastal, as in, right on the the coast. The constant supply of flotsam and driftwood meant we had all kinds of ropes, cordage, containers, nets, enough timber for fires (making sure to take the dry stuff from wayyyyyyyyy up above the normal tide line) not to mention the easiest pickings for food.
We ended up moving into the carcass of a wrecked yacht which seemed like the Ritz after various lean-to's and similar shelters. Also keep in mind that the larger a shelter is the more it takes to heat it.
If you can't be hassled to read either of the above two linked threads I will summarise the likely major issues as follows, ignoring the legal issues for now, and in no particular order of importance:
1. carrying enough of the right kit
2. shelter
3. warmth (fire, shelter, adequate/proper clothing
4. storage (food, water, kit)
5. hygiene
6. medical care
7. replenishing worn, broken, or lost kit/supplies
8. exit strategy
The constant thorn in anyone's side assuming the basic requirements of shelter and warmth are taken care of is ensuring an excess food supply and then solving the problem of storage of the excess. Refrigeration is not an option and canning requires a lot of heavy and bulky kit and knowledge, so unless you put yourself in an environment where refrigeration is an option you have no reliable way of storing foodstuffs safely that won't introduce other issues. You can't just smoke or dry everything, for example, ecause you still need storage for the end product. Even pemmican requires two luxuries - fat and a container.
Water - processing and storing. Enough said.
Hygiene is desperately important otherwise you're going to be your own worst enemy. Ignoring the high risk of self-introduced dysentery (or worse) I would include in personal hygiene the much underestimated looking after your appearance because, quite simply, if you look alike a down and out you will be treated like one and, sad to say, this is likely to hasten your being 'encouraged to leave' an area.
You will, at some stage, require stuff. Without income that stuff will be hard to provide.
At some stage it is likely that you will return to mainstream society and so your exit strategy (from the wilds) needs to include a rough plan on how you might reintegrate.
If we flip the coin over, you could take a look at the other side which could be more viable. Partly self-sustain while working seasonally and/or in exchange for the use of a bothy or similar facilities. Look at ways of ensuring your ongoing health (and wealth) by utilising the lifestyle.
Example: a mate of mine did this (and still is, many years later) by turning rabbits into a cash crop at farmer's markets. He sells them chilled or frozen, all butchered and wraped in clingfilm (for the fresh ones) or vacuum sealed for frozen.
He looks after a lot of land and got fed up with game dealers dropping their prices to 30p a rabbit. He sells them for a pound or two a piece, but he compliments this by also selling various pre-prepared sauces and free, give-away recipe sheets that can be used to help folks prepare their rabbits.
Lambing requires some experience (which can be got for the price of volunteering for a couple of seasons) but once you know what you are doing that sort of skill can get you regular, seasonal work which will also put you right into the network of people you need to keep onside to live in the countryside. If you talk to them properly and are seen as being responsible and trustworthy your name will be noised about with neighbouring farms and offers of casual work, beating, pest control and so on will filter your way.
Country folk are a tremendous asset to anyone planning anything like this, but they will be your biggest enemy if you are seen to simply be on the take from them.
Tread carefully.
Done properly you could live on the fringes of society on your own terms in wonderful areas surrounded by a support network of friends (given time) and like minded (on some points) individuals.
Done badly you could be injured, ill, or sent up the river as poacher.
I wish you the very best of luck with it.
