there's a long and short version to make seitan, both of which use soy sauce, so just insert your sauce alternative, since it's just for flavoring you could just add more garlic or any other seasoning. Or, since so many vegetarian recipes call for soy sauce and tamari, you could try this: http://www.japan-101.com/forums/archive/index.php/t-27.html
12 cups (4lbs) whole wheat flour
3 1/2 quarts water
Put flour in large bowl and add enough of the water to make a soft dough (about 5 cups or so). Knead this for 5 minutes, then add enough water to cover your dough and let it rest 15 min.
While it rests, boil together:
1 onion cut up
1 crushed garlic clove
small piece of kombu
1/2 cup of soy sauce*
2 Quarts water
After your 15 min. are up, put the bowl in the sink and knead until the water turns starchy - drain off that water and cover the dough with fresh water and knead again. You keep doing this until the water is almost clear. Now you have a raw seitan "roast". You would stop here if your recipe calls for raw, otherwise make 3 equal pieces and add to the pot to simmer for 1 hour do not boil!
it has to cook long and slow to get the meaty texture.
In a saucepan, bring 4 cups water, 1/4 cup soy sauce*, and a piece of kombu to a boil, meanwhile:
In a large bowl, mix:
2 cups whole wheat flour
1 tsp garlic powder
1 tsp ginger powder
In a large measuring cup, mix:
1 1/4 cups water or veggie stock
3 TB soy sauce*
1-3 tsp sesame oil
Add the liquid to the dry ingredients, knead 10-15 times and let rest 5 min. Knead again and let rest 15 min. Cut into 6-8 pieces and stretch into cutlets or desired shape and simmer in broth for 1 hour do not boil!
Only the long version is really wheat gluten, the short version is more like a meaty pasta since it still has all of the starch.
Hope this helps!
I'd also like to second the bean burgers!
Edited to add: Flax is great, but make sure it's milled (ground) because people have trouble digesting the hull and getting the goodness out of the seed.