Soak 5 to 6 strips of kombu, 8 to 12 inches long, for several minutes, or until they are soft enough to cut. Slice into 1-inch squares, or 1/4 inch strips that are about  1 1/2 inches long. 

Place in a saucepan and cover with a mixture of 1/2 cup of shoyu soy sauce and 1/2 cup of water. Bring to a boil. Cover and reduce the heat to low. Simmer until all the liquid evaporates, about 30 to 40 minutes. 

Cool off and store in a glass jar.