I think the first thing you would need to do is establish the power Jack exerts over the boys through obtaining meat and offering it to them, therefore meeting their most basic needs of survival. Because he lets them eat until they can not hold any more food through the...
I think the first thing you would need to do is establish the power Jack exerts over the boys through obtaining meat and offering it to them, therefore meeting their most basic needs of survival. Because he lets them eat until they can not hold any more food through the meat he has obtained, they shift their allegiance from Ralph to Jack:
“Give me a drink.”
Henry brought him a shell and he drank, watching Piggy and Ralph over the jagged rim. Power lay in the brown swell of his forearms: authority sat on his shoulder and chattered in his ear like an ape.
There are a couple of literary devices here. First, the imagery of power laying in his forearms shows that Jack is physically strong and now also strong in leadership. The quote ends with personification, showing how Jack's authority seems natural now, and a simile through the use of "like an ape."
Jack then orders everyone to do "our" dance, chanting for blood until the boys are worked into a frenzy. When Simon stumbles out of the forest, Jack's group murders him:
The sticks fell and the mouth of the new circle crunched and screamed.
This is Jack's leadership, and by extension his call for death. The metaphorical use of the word "mouth" is used to convey how the boys devour Simon like beasts themselves. They "crunch" and "scream," uttering no words, but acting in a passionate hate toward the outsider just as Jack has trained them. They have become blind to the truth because Jack has become so singularly focused on blood and death.
After Piggy's death, Jack proudly takes responsibility for what has transpired:
Suddenly Jack bounded out from the tribe and began screaming wildly.
“See? See? That’s what you’ll get! I meant that! There isn’t a tribe for you any more! The conch is gone—”
He ran forward, stooping.
The imagery in how Jack relays this information is important. He "bounds" from the tribe and "scream[s] wildly." This furthers the idea of his savagery in leadership. Roger is fully aware that his actions would be appraised favorably by his savage leader; thus, Jack is ultimately responsible for Piggy's death.