Wikipedia
A hay box, straw box, fireless cooker, insulation cooker, wonder oven or retained-heat cooker is a cooker that utilizes the heat of the food being cooked to complete the cooking process. Food items to be cooked are heated to boiling point, and then insulated. Over a period of time, the food items cook by the heat captured in the insulated container. Generally, it takes three times the normal cooking time to cook food in a hay box.
Usage examples of "haybox".
Creek, the Haybox Fight, Washita, Slim Buttes, Palo Duro Canyon, Rosebud, Bear Creek, Wounded Knee.
Nothing to leave but a brooch, some chairs and a table, a prized haybox oven, and his slave.
Fear flares up in a blaze: holy night, a holy roll in the Austrian hay, where tales are told of the holy animal come to eat at the haybox of social welfare.