You can learn to make soy sauce at home rather than buying the store-bought variety. To do so, you'll usually need just a few basic ingredients, including soybeans, flour, water and salt. Making soy sauce typically is a long process, however. It will take at least a couple of weeks and might take a few months. The extended waiting time from preparation to consumption allows the soy sauce to ferment properly.
To make soy sauce, you'll usually have to start with the soybeans, which make up the body of the soy sauce. You can start with boiling the soybeans until they are soft and then removing them from their pods. At this point, chop the soybeans into small pieces and put them in a bowl that has enough room for the addition of flour.
Your next step to make soy sauce is pouring flour into the soybean bowl. You'll need to mix the soybeans and flour together until they appear to be combined well. Place the mixture on a flat surface and knead it into a dough-like form. Finally, you'll need to form a cylinder-like shape out of the dough and slice the form into small disks.
To complete your soy sauce preparation, you'll have to add mold, which is necessary for the fermentation process. You can grow your own mold to use when you make soy sauce by moistening a few paper towels with water and placing them on a flat surface. You can then place the cut pieces of soybean-and-flour dough on top of the paper towels and cover them with more moistened paper towels. To allow mold to form, you'll need to allow this mass to sit, wrapped in plastic wrap, until the paper towels are well covered in mold.
After the paper towels become moldy, peel away the plastic wrap and place the soybean dough on a plate or tray in the sun. They'll need to remain there until they are dry and brown. Then, you'll need to place the dough disks into a pot of one part salt and 16 parts water and cover it, allowing the liquid to sit until the dough disks have dissolved. This could require weeks or months of waiting, and you'll usually have to stir the pot on a daily basis. When the dough dissolves, you can strain the soy sauce and transfer it into bottles.