Place the chickpeas in the bowl of a large food processor. Blend them alone until they become powder-like, scraping down the sides as needed. Add the parsley, cilantro, onion, garlic, flour, salt, coriander, cumin and black pepper and blend until the mixture turns to paste. Cover the bowl and refrigerate for 1-2 hours to set. When ready to make, sprinkle baking soda on the falafel mix, and fold in gently.