Mix the ground flaxseeds in 6 tablespoons of water in a small bowl and set aside for 5 minutes, until it thickens, making sure the water is completely absorbed.
Preheat the oven to 400 degrees F.
In a large bowl, mash the black beans with a potato crusher. Add corn, oatmeal, sunflower seeds, celery, onion, lemon juice, olive oil, poultry seasoning, garlic, salt, and cayenne pepper.
In a small bowl, use a fork to mix the miso and water together to form a loose paste.
Stir in the paste and stir well until the batter comes together. It is possible to mix the mixture with a large spoon or the potato masher while mixing at the same time.
Using half a cup, remove the batter, press firmly, and shape into a ball. Place on the baking sheet lined with parchment paper and form a 1 inch (2 cm) patty, tapping over it. Repeat until the batter runs out. If your hands get too sticky, wash and dry them before you continue. Bake the patties and cook for 20 minutes. Turn over and continue cooking for 10 minutes, until the desired texture is reached.
Serve on a lettuce leaf or hamburger buns with slices of vegetables and condiments.