In your slow cooker, add 1 tablespoon of olive oil. Turn to high setting.
Mix together the cornstarch and paprika in a large bowl. Add the seitan pieces and mix to coat. Put the coated seitan into the slow cooker.
Put the orange juice, peel, soy sauce, vinegar, sesame oil, ginger, remaining oil, and garlic into a medium bowl and mix well.
Pour the sauce over the seitan, making sure that all pieces are coated.
Add the vegetables. Cook on high for 2 hours, then check for doneness. Vegetables should be tender. It might need another 30-60 minutes, depending on your slow cooker.
Divide onto plates and add garnishes. Delicious served over brown rice.