Preheat oven to 300 degrees. Combine seeds, oil, chili powder, tamari, and garlic powder in a sealable 1-gallon plastic bag. Seal the bag and knead to coat the seeds with seasonings. Remove from the bag and spread the coated seeds on a baking sheet in an even layer.
Bake for 15 minutes, then turn the seeds over. Continue baking seeds until lightly toasted and fragrant, about 15 more minutes. Remove from the oven and sprinkle lightly with salt. Cool before serving, store in an airtight container in the refrigerator.