After draining and rinsing the beans, spread them on a towel and pat them dry. For even better texture, let them air dry for 20–30 minutes or roast them on a baking sheet at 350°F (175°C) for 10–15 minutes to remove excess moisture.
In a food processor or blender, combine the beans, garlic, tomato paste, vinegar, and mustard. Pulse until mostly mashed with some bean texture remaining.
Add the green onions, parsley, oregano, salt, and pepper to taste, and process to break up and blend. Add the oats and 1/2 cup chickpea flour, then pulse until just incorporated.
Transfer the mixture to a large bowl and stir in the olives, corn and red pepper.
Let it rest in the refrigerator for at least 1 hour, or even overnight. The oats and chickpea flour will absorb excess moisture and make the patties much firmer before shaping.
After resting for 1 hour, check the texture. It should feel like a mixture you can scoop and shape. If it is still wet, add another 2–4 tablespoons of chickpea flour or oats and let it sit another 10–15 minutes.
Shape into patties with your hands.