The setting plays a major role in this novel. The boys are basically stranded on an uninhabited tropical island, presumably somewhere in the Pacific in the 1950s. It is an environment which is completely alien to them, and after initial boyish enthusiasm the grim reality of a life devoid of adult supervision in a strange, threatening world begins to set in.
The island contains thick jungle and dense undergrowth with plentiful food on offer through wild fruit and pigs which roam. Most of of the story centres around the white beach at the lagoon area on the island,
...the white surf flinked on a coral reef, and beyond that the open sea was dark blue. Within the irregular arc of the lagoon was still as a mountain lake.... (p.14)
In their initial exploration, the boys gain a good understanding of the geography by climbing to the top of a mountain. In the distance they see a part of the island that later Jack and his breakaway group will use,
There, where the island petered out in water, was another island; a rock, almost detached, standing like a fort.... (p. 38)
They are also able to look back at the point where they all met at the beach (fringed with palm trees) and note that the entire side of the island there is enclosed by a coral reef.
The boys are initially wildly enthusiastic about being in a place which no doubt is the stuff of their adventure storybooks. Slowly however the setting begins to tear them apart and in the absence of adult supervision, bring them down to a primeval state. The isolation, the tropical heat, the need to hunt wild animals and the inability to make logical sense of what seem like phantom occurrences all take their toll on the formerly 'civilized' British boys.
Golding has chosen a perfect setting for a tale which points out that man's savage inner being lurks not far beneath the surface.