Cook soybeans for 1-1½ hours, then add the soybeans to a food processor and blend to a paste.
Pour pureed beans into a bowl and combine with flour. Place the bean-flour mixture on the clean surface and shape it into a log. Then cut the log into slices about ¼-inch in thickness. Arrange the soybean slices on a moist paper towel and cover them with another paper. Leave it to sit for seven days.
After a week, arrange them on a baking sheet and leave them to dry.
The next part is fermentation. So, take a pot, pour water and salt, stirring to combine. Add the soybean discs and cover. This step aims to dissolve the discs in salt water, which can take up to 6 months.
Stir the mixture daily. The discs should dissolve in salt water, which can take up to 6 months. It is important to stir the mixture daily.
Finally, when the soybean slices have completely dissolved, strain the mixture with cheesecloth into bottles for storage. Now, the soy sauce is ready for use.