Toast the coriander seeds and cumin seeds in a skillet over medium heat until lightly browned and fragrant, then coarsely grind in a spice grinder.
In a food processor, combine the cumin, coriander, soaked chickpeas, onion, garlic, cilantro, parsley, baking soda, cinnamon, salt, a few turns of black pepper, the crushed red pepper, flour, and lemon juice and pulse quickly, 80 to 100 times, until the mixture is combined, but still slightly grainy.
In a large skillet, heat 1/4 inch oil over medium-high heat until shimmering but not smoking. Fry a 1-tablespoon test patty until golden and then taste it. Adjust the seasonings in the mixture as desired. Form balls of falafel mixture, 3 tablespoons each, packing them firmly and then flattening them slightly. Fry on all sides until golden brown. Transfer to a paper towel.