Piggy suggests using his glasses to start a fire by focusing the sunlight, rather than relying on the unreliable matches. He believes this method will be more efficient and effective in ensuring their rescue.
Piggy is the voice of reason in chapter 2 because he insists that they make a fire so they can be rescued. Also in this chapter they use his glasses to light the fire.
one of the little kids was not there and he thinks he was caught in the forest fire.
By Piggy's glasses and the sun reflecting off them
In chapter 2 of Lord of the Flies, the boys start the fire by using Piggy's glasses to focus the sun's rays onto dry leaves and twigs. This method allows them to create a flame and start the fire for a signal to potential rescuers.
Piggy suggests building the fire on the beach by using the lenses of the boys' glasses to focus the sunlight and start the fire. He recommends using the lenses like a magnifying glass to create the fire. Eventually, they successfully build the fire on the beach.
Because in the end of the chapter, Jack's tribe attacks Ralphs tribe. Piggy thought they were after the conch (The Shell) but instead, they stole Piggy's glasses for fire usage (The Glasses)
Piggy proposes to move the fire to the beach, away from the mountain, to avoid it going out and losing the chance of being rescued. He believes the fire is more useful and visible on the beach as a signal for passing ships or planes.
Well in chapter 10 Jack and his tribe of savages invade Ralph's tribe (made of up Ralph, Sam and Eric, Piggy, and one/two littluns) in order to steal Piggy's glasses, which is overall the power to start a fire on the island. Jack might have mentioned this plan in chapter 9 so I'm hoping this is the right answer to your question.
The boys use his specs(glasses) to direct the sunlight to the sticks on the mountain and make a fire.
In "Lord of the Flies," Piggy's glasses are taken in chapter 2, on page 40 in the 1999 Penguin Books edition. The boys take Piggy's glasses to start a fire.
Jack solves the problem of making fire by stealing Piggy's glasses, using them to start a fire and cooking meat. He disregards Piggy's suggestion of using the glasses for rescue signals, instead prioritizing his desire for power and control over the boys.
Ralph said that near the end of chapter 2: Fire on the mounatin when Piggy admitted that he didn't know the names of the littluns.