I've been hesitating to answer this because I can't think of any source that says in so many words "of course, a lord couldn't simply take land away from someone". Then I realized that there's no canon law that says "the Pope cannot sacrifice unbaptized boys on the altar during Easter Mass", either.

I've just re-read Magna Carta, the original version sealed by John ... well, the English translation thereof. After the first clause, the one about the church, the next 7 are all about preserving inheritances, of the normal heir and of the widow. Showing so much care about inheritance shows how much more important possession is.

And indeed possession of land is later protected. Clause 39 (in Warren's numbering) is "No freeman shall be ... disseised [lose land] ... or in any way destroyed ... except by the lawful judgement of his peers and by the law of the land." Clause 43 says that if a fief is escheated to the crown, their tenants shall hold by their old conditions. Clause 51 deals with any who have be dispossessed. So too with clauses 56 and 57 for Welshmen.

Land was critically important -- consider that it's now called "real estate" or "real property". Some was supposed to lose land only through laborious proceedings of right (or self-help by taking back rightful land by force of arms, but that was later curbed and suppressed).

Even attempts by the king to constrain privileges, like later proceedings of quo warranto (or more unsystematic ones under Henry II) to make men justify their franchises and privileges, or enforcing forest law on royal lands, stirred up a lot of unrest.

What the king granted was whatever was in his hands. The title was, either by reviving an old title or by creating a new one. At least in Anglo-Norman times, an earl got the title of a shire, could sit in the shire court with the sheriff and the bishop, and got the third penny of justice, one-third of all fines assessed in the shire. Other things would often enough be given with it -- castles, manors, mills, parks, whatever that the king already held, privileges and franchises that were governed by and conceded by the king.

How did the king get titles and lands to grant? Maybe no king had given it before -- I think William the Conqueror kept about a third of England in his hands. Or a lord could die without an heir, in which case, his lands and titles were "escheated" to his lord, which often was the king. A lord could be "attainted", deprived of lands and titles, due to treason (meaning he lost the rebellion; as later famously observed, if he won, it wasn't treason) or other major felony.

A fief in the king's hands usually had tenants, whether serfs, freemen, sergeants, knights, and/or lords. If the fief were being regranted, they would likely be granted with them.

I don't have examples of grants by charter or letters patent to hand to point to. Generally, a charter at least was very detailed in listing exactly what the donor was giving to the recipient, just to avoid later questions about who had the privilege of the fair of Saint Frithfrith, or the mill on the River Plunk and the right to force the locals to use it, or the court of the hundred of Doddering Sloughleigh.

There were edge cases. There might be a charter of confirmation. A lord might die without a male heir but with a daughter: the title and possessions might be confirmed to the daughter's husband.

Certainly no later than the restoration of Charles II and the act removing all jurisdiction from noble titles, noble titles were completely honorary; any lands or other possessions would be given separately. I don't know when the transition happened.