There are plenty of contrasts available in Golding's novel.
1. Ralph''s style of leadership contrasts with Jack.
2. The beauty of the island is contrasted with the destruction and savagery of the boys. The "scar" is an ugly mark on an otherwise beautiful island.
3. Roger's pure evil may be contrasted with Simon's respect for all of God's creatures.
4. Hunters may be contrasted with Ralph's group.
5. Savagery is contrasted with civilization, thought, and rationalism.
6. Young ones are contrasted with old kids.
7. Past civilization and manners are contrasted with the boys' new ones.
8. The adult world is contrasted with the child's world.
9. The actuality of the beast is contrasted with the boys' perception of a mythical beast.
Whereever there are opposites, there are contrasts. The novel is replete with them.
Yes, I think he probably does. It's not like the whole novel is built entirely around contrasts, but there are key contrasting dynamics set up in the play.
For example, you might juxtaposes Ralph with Jack as symbolic of one of the central contrasts in the novel. Ralph as a chief believes in democracy: he enforces assemblies and the conch, and allows everyone to speak. He wants everyone to vote on key decisions, and his priority is to keep the signal fire lit in order that the boys might get rescued.
Jack, on the other hand, believes in a dictatorship:
“Conch! Conch!” shouted Jack. “We don’t need the conch any more. We know who ought to say things. What good did Simon do speaking, or Bill, or Walter? It’s time some people knew they’ve got to keep quiet and leave deciding things to the rest of us.”
You can pretty much contrast what Jack believes against what Ralph believes. So Jack believes in tyranny, Ralph democracy. Ralph believes in signal fires, Jack believes in hunting. Ralph believes in assemblies, Jack in dances and pig-hunting. Ralph is associated with the conch, Jack with the symbol of a sharpened stick. Ralph is advised by Piggy, an outsider but with a heart of gold and true wisdom, Jack is advised by Roger, an outsider but with a cruel, sadistic streak. And so on.
Yet let me make one caveat to this. It's not as absolute as that: Ralph too is drawn to the hunting and the pig-killing (he, of course, is involved in the murder of Simon). Jack doesn't start off obsessed with hunting - he initially acknowledges the importance of the signal fire. So the contrasts are not black and white. But they're definitely there to be found.