Preheat oven to 350°F (175°C).
Blend wet ingredients: Add everything except the vital wheat gluten to a food processor. Blend until completely smooth.
Add vital wheat gluten: With the processor running, add the vital wheat gluten one spoonful at a time through the chute until a dough ball forms.
Knead in food processor: Run the food processor for 2–3 minutes to knead the dough ball, until it is smooth, soft and stretchy.
Shape the seitan: Form the dough into a ball, then divide into 4 equal pieces. Shape each into fillets about ¾–1 inch (2–2.5 cm) thick.
Prepare the dish: Oil a 9x13-inch (23x33 cm) glass or ceramic baking dish. Place the fillets inside and coat all sides with oil. Add 2 tablespoons of water to the pan, then cover tightly with foil.
Bake covered: Bake at 350°F (175°C) for 30 minutes. Remove from the oven, flip the fillets, add the remaining 2 tablespoons of water, cover again, and bake for another 20 minutes.
After baking for 50 minutes, coat the fillets with your spice rub of choice and bake at 425°F (220°C) for 10-15 minutes to brown.
Let rest at room temperature for 10 minutes. Slice, shred, or serve as fillets.
