Cooking in an imu is an ancient Islands custom that requires much work and cooperation among family members. Preparations begin several day before Thanksgiving, when the family goes down to the beach or to the mouth of a stream to fill sacks with smooth, rounded lava stones. They choose the stones carefully for their shape and size and for the presence of holes that will prevent the rocks from exploding when they are heated.
To prepare the imu, the men first dig a large hole in the shape of a bowl about three feet wide and two feet deep. They then line the bottom and side of the hole with the lave rocks. Firewood is cut and piled up, ready for the holiday morning when a first is lit inside the hole.