The hay basket (or cooking basket) is an ideal way to keep food warm or to finish the cooking process. The hay basket is a braided basket made of locally available plaiting materials (hay, reed, grass, bamboo). The plaiting materials are lined inside with fabric, filled with cotton or other insulating materials). Depending on what is locally available like: (chicken) feathers/down, hay/grass, millet chaff, (sheep) wool, rags and even used plastic bags.
As long as the basket insulates sufficiently and retains the heat.