Lord of the Flies, by William Golding, is full of characters who recall things about their pasts; for example, the little boys want to build a television set, something they obviously enjoyed in their lives before being stranded on this island, and Piggy thinks about his "auntie" who used ot give him sweets all the time. The boys also have a lot of nightmares, and undoubtedly some of those are based on remembering things from their past as well as some of the horrors they are currently living. The only actual flashback in the novel happens to Ralph.
In chapter seven, Ralph is unhappy with the direction things are heading and, though he is leader, he feels powerless to do anything about it. Eventually he sits down, leans against a tree trunk, and flashes back, with great clarity and specificity, to what his life used to be like.
He recalls a time when his mother was still alive and before he was sent away to boarding school. He remembers ponies, snow, the hiss of the tea kettle, corn flakes with sugar, and his books.
Vividly [these memories] came before him; he could have reached up and touched them, could feel the weight and slow slide with which The Mammoth Book for Boys would come out and slither down. . . . Everything was all right; everything was good-humored and friendly
Of course, his quiet reverie is soon interrupted by a noisy group of hunters crashing through the jungle next to him as they hunt a pig.
Im not quite so sure about the others but Ralph does have a flashback of the times he used to have decent food, books, snug bed, etc..