Seasoning advice for seitan to replicate gyro meat

Bury it in bread. A meat-substitute burger or kebab meat that has obvious textural or flavor flaws when served bare will often appear near perfect in a pita or bun. Also, you can keep a lot of oil/sauce on it that way, which carries seasonings and juicyness.

Start with baked seitan, made from vital wheat gluten (and 10-20% of another protein flour like lentil or chickpea optimally), and season both in the dough and when sauteing the cut up seitan later - experiment with which seasoning is best added at which time.

Try strong soy sauces (eg chinese light), cumin, smoked salt and/or smoked paprika, sugar, nutritional yeast/msg, flavorful chile pepper powders (eg turkish chile flakes - not just cayenne pepper powder!), garlic, onion. Also add something acidic, eg sumach or lemon.

Fat is your flavour carrier. Seasonings should be well infused into your choice of fat/oil. Consider experimenting with dark sesame oil or walnut or pumpkin seed for part of the fat. I even add a drop or two of sichuan pepper oil to many 'meaty' dishes for added depth. One restaurant's terrific chili relied on old french-fry oil, though I don't recommend that, but gives an idea of the importance of flavourful fat.

Another meaty note to consider is cooking on iron or a few drops of beet juice in the making of gluten dough. I have even added a few mineral-supplement drops to get that heme-like flavour

When preparing seitan I found out that the best way to "flavour" it is to prepare is on steam without previously removing starch (so no washing the starch out is needed). So it's steamed out in the process (usually around 40-50 minutes).

To get THAT (I mean any type of meat prepared in special way) particular flavour I mix the dough with spices used in meat in ratio: 25% more spices than required in meat. Also for some spices like cumin and/or rosemary I add a handful/teaspoon to the boiling water.

For 1 kg of gyro seitan I would use

1,25 tablespoon minced garlic (if using flakes or granulated one use 3 spoons)
1,25 teaspoon dried oregano (if your oregano have a lot of flowers in it use 2 spoons)
1,25 teaspoon ground cumin (frying cumin on dry pan give it more kick)
1,25 teaspoon dried marjoram
1,25 teaspoon ground dried rosemary
1,25 teaspoon ground dried thyme
1,25 teaspoon ground black pepper
half teaspoon sea salt (for the meat, second half should go into water)
one onion
Finely cut onion should be fried with two spoons of oil. Leave the pan on the side. When Seitan is ready put it onto the pan and let it simmer on low heat so it will absorb all the oil and get a little burned on sides.