Itaewon in Seoul has long been the centre for African and halal groceries, and several shops there carry maize meal, cassava flour, dried fish, plantain and the spice mixes that make food taste right.
Ansan — particularly around the multicultural street — is the other significant hub, and often cheaper.
Outside Seoul and Ansan it thins out fast. Members in Daegu, Gwangju and Busan generally order online or arrange a group order when someone is travelling to Seoul anyway.