The chapter in which Huck enacts his escape is Chapter Seven, so you would do well to re-visit this chapter to remind yourself of the central facts of Huck's plan. Let us just remind ourselves that Huck manages to escape the hut where Pap has locked him, then conceals his manner of escaping. He then fakes a violent entry and his own death to ensure that Pap and others will think he has been killed and that nobody will bother looking for him, so he can be left in peace. Note how he does this:
I took the axe and smashed in the door. I beat it and hacked it considerable a-doing it. I fetched the pig in, and took him back nearly to the table and hacked into his throat with the axe, and laid him down on the ground to bleed; I say ground because it was ground--hard packed, and no boards. Well, next I took an old sack and put a lot of big rocks in it--all I could drag--and I started it from the pig, and dragged it to the door and through the woods down to the river and dumped it in, and down it sunk, out of sight. You could easy see that something had been dragged over the ground.
Thus we can see that the shrewd nature of Huck's plan lies in the way that he has conveniently done away with himself, making it seem that he has been murdered and killed, therefore allowing him to escape and to finally gain the freedom that he has desired for so long. Huck, after all, could have just left the hut and ran away, but doing it this way means that he will not be bothered by his father any more.