 Traditionally this is done over the straw generated as a by-product of the rice harvest.Sawachi is a term which refers to "a style of meal" in Kochi prefecture, according to Kochi-City Tourism Association.It says that the characteristic of the style of eating is "its freeness in the arrangement of food on a large dish" 
People eat Sawachi in the situation of "Enkai" which refers to a gathering of family, friends and relatives.