Using a food processor, blend the cooked chickpeas with onion, garlic, fresh herbs, cumin, paprika, baking soda, flour, salt, and pepper. Pulse until the mixture is combined but retains some texture. Chill in the refrigerator for 15 minutes to firm up.
Shape the mixture into small patties, roughly 1.5 inches in diameter. Warm olive oil in a skillet over medium heat, then fry the falafel for about 3–4 minutes per side until they turn crisp and golden. Transfer to a paper towel-lined plate to drain excess oil.
For the tzatziki sauce, mix Greek yogurt with grated cucumber, minced garlic, lemon juice, olive oil, and chopped herbs. Stir well and season to taste with salt and pepper.
Lightly warm the flatbreads before assembling. Spread a generous amount of tzatziki onto each. Layer on the falafel, followed by shredded lettuce or mixed greens, halved cherry tomatoes, pickled onions, sliced radishes, and crumbled feta.
Finish with a sprinkle of fresh herbs and an extra drizzle of tzatziki. Depending on the type of flatbread, either wrap or fold before serving. Enjoy immediately!
