1) Drain chickpeas and mash them in a bowl with a fork. Some chunks are okay.
2) Toast cumin and coriander and then grind (or use ground spices) Add spices to chickpeas.
3) Stir in veggies, parsley, and olive oil to chickpeas and add enough flour until the mixture sticks together (2-4 tablespoons).
4) Form small patties, about two tablespoons, out of the mixture and flatten it slightly. Add patties to a baking sheet with parchment paper. Drizzle with olive oil.
5) Bake falafel at 350 degrees for 20 minutes, flipping once halfway through.
6) Meanwhile prepare toppings and mix together tzatziki sauce.
7) Stuff falafels in warmed pita and drizzle in sauce and stuff with veggie toppings.