Combine in a large bowl:
Mix until the dry ingredients are completely moistened, then knead the dough until firm and well combined, about 5 minutes. Form the dough into a log and cut into 1- to 2-inch cubes or chunks. Bring to a gentle simmer in a medium saucepan:
Add the seitan pieces, cover, and simmer gently for 45 minutes. The pieces will swell above the level of the stock (this is normal). Remove the seitan from the broth with a slotted spoon if using right away. Let cool slightly, then squeeze to remove some of the liquid the seitan has absorbed. Or, let the seitan cool in the pan, transfer to a container, add broth, and store covered in the refrigerator for up to 5 days.