I never did this topic but I'm helping my brother out, and ADORE Lord Of The Flies.
I would say that belonging is in several different areas:
SYMBOLS AND THEMES:
The Conch
Sense of order and an idea of belonging to a GROUP as the noise is used to bring them together, and it allows someone to talk. As we see, the group breaks down. The sense of belonging in each of them breaks down with the climax of the Conch breaking. Respect is seen as important to a sense of belonging as the Conch is eventually somewhat disregarded at meetings, and this is when they begin to feel alone and desolate and chaos ensues.
Choir:
These boys are the epitome of conformity at the beginning. Order, walking in lines, standing to attention... but it is as the order around them breaks down that it breaks within their group as well.
Civilization:
This is belonging to the controlled world, one that they are now removed from. In my opinion it brings up an interesting point about how a sense of belonging can be removed, when a person is taken geographically from that place. It also suggests that proximity is what causes us to belong, but also causes us to break apart. Ralph shows the order that appears to be almost separate to some of the others, but it shows that perhaps to create an environment that is conducive of belonging there must be someone prepared to step up.
GENERAL:
If anything, at it's most basic, it suggests that we all belong to the human race. Or even to an animal classification. It shows us to be one with everything we strive not to be, to be as evil, as beastly and as brutal as animals. The beast inside them, that they are all terrified of, connects them. We belong as living beings, we are one in that physical instinct to survive. Perhaps the book questions whether this is the only thing we have in common with each other, and perhaps it questions whether the sense of "belonging" we have created in our "civil" world, is actually existant, or if it is a flimsy facade that can crumble around us, leaving us alone and scared.
The diversity of the characters also suggests how belonging can exist despite our differences, but this is also cut down to show that, in instinct, we are all virtually the same.