How to Build an Imu (Hawaiian Earthen Oven)
The traditional way to cook a pig for a luau is to put it in an imu or earthen oven. Hot rocks called pohaku are covered with wet vegetation that steams the buried food slow cooking it for hours. There are more permanent versions of an imu around. Serious people build an imu pit in their yard with a concrete bottom for reuse. Ornate holes in the ground may be carefully lined with lava rock as if an ancient Hawaiian mason built it.
An imu has a few basic layers starting with the bottom:
Wood fired rock surrounded by burning embers
Wet vegetation
Food
Cover