Place the lentils and 2/3 cup oats in a medium pot with the broth and water. Bring to a boil over high heat then reduce heat to simmer and cover the pot. Cook, stirring frequently, until the liquid is absorbed and the lentils begin to break down a bit, about 40 minutes. If necessary, add up to ½ cup more water to avoid scorching. The mixture should be very thick and sticky. Remove from heat and stir in the miso, tamari, onion powder, paprika, basil, and flaxseed. Set aside.

Over medium heat in a nonstick frying pan, toast the almond flour, stirring constantly until golden brown. Remove from the pan and set aside. Add the oil, onion, and garlic to the pan and sauté over medium-low heat, stirring frequently, until the onions are deeply golden, 12-15 minutes.

Add the onions to the lentil mixture and stir in the remaining ½ cup oats. Mix well. Cover and let sit for 15-30 minutes.

Preheat the oven to 350ºF. Line 2 baking sheets with parchment paper.

Using a large ice cream scoop or 1/3-cup measuring cup, scoop the mixture onto the baking sheet and flatten into patties about ½-inch thick. Bake for 25 minutes, then gently flip the burgers and bake another 10-15 minutes, until brown and crisp on the edges.