Drain the beans, then mash them roughly with a fork.
Add the garlic, grated courgette, dried oregano, flax egg, lemon zest, parsley and salt and pepper. Combine well.
Add half of the chickpea flour, and mix with your hand. Add more flour until you get a dough-like, sticky mixture that combines well.
Make 4 balls and flatten these between your palms. Put them on a tray, lined with baking paper. If you have time, chill for 30 minutes.
Preheat the oven to 190°C or set it to grill.
Spray the patties with olive oil, then put the tray in the oven. When the patties look brown and crispy, turn them over and grill or bake until this side looks done too.
Serve warm.