Drain and rinse the beans. Shake the excess water off and spread them out on a large baking sheet. Mash most of them with a potato masher or fork and leave them on the tray to air dry for now.
Create the flax mixture by stirring together the ground flaxseed with warm water. Set it aside to thicken for about 5 minutes.
Heat a large skillet to medium-high and then add 1 tbsp of oil. Sauté the onion and pepper slices for 3-4 minutes or until they're soft.
Add the beans to a large mixing bowl. Finely dice 1/3 cup of the peppers and onions and add them to the bowl. Add the cilantro, flax seed mixture, green chilies, garlic, seasoning, and barbecue sauce. Stir everything together until it's well combined.
Next, stir in the oat flour by cutting and smashing it into a dense mixture. Form 8 patties by scooping 1/3 cup of the mixture, roll them into balls, then press them into 1/2 inch tall discs on parchment paper.
Let the patties sit for 10 minutes. This will help them hold their shape better and give time for oat flour to absorb excess moisture.
Heat the large skillet to medium and then add 1 tbsp of oil. Cook the burgers for 4-5 minutes on each side until they're crispy and slightly charred.
Assemble your burgers with avocado, sautéed onions and peppers, cilantro, green chilies, and any other favorites.