Heat the stock to a light boil over medium-high heat. Add the tempeh to the stock and simmer for 25 minutes. Drain and let cool to room temperature for 15 minutes. Once cooled, grate tempeh into a large bowl.
In a small bowl whisk together the soy sauce, lemon juice, garlic and seaweed flakes. Pour the seaweed mixture in with the grated tempeh and stir until well mixed. Mix in the red onion, celery and dill pickles. Toss with the mayonnaise. This salad can be served immediately, but is best when chilled for several hours to allow the flavours to blend.