Lentil barley soup

1 cup lentils, rinsed

1/2 cup hulled or pearled barley

6 cups water or vegetable stock

1 onion, chopped

2 garlic cloves, pressed or crushed

2 carrots, sliced

2 stalks celery, sliced

1/2 teaspoon oregano

1/2 teaspoon ground cumin

1/4 teaspoon black pepper

1 / 8-1 / 4 teaspoon red pepper flakes

1 / 2-1 teaspoon salt