Preheat the oven to 375°F and line a baking sheet with parchment paper.

In a food processor, combine black beans, walnuts, breadcrumbs, onion, and garlic. Pulse until the mixture is coarsely ground.

Transfer the mixture to a bowl and add soy sauce, tomato paste, oregano, thyme, fennel seeds, red pepper flakes, salt, and pepper. Mix until well combined.

Using your hands, form the mixture into 1-inch balls and place them on the prepared baking sheet.

Bake in the preheated oven for 30 minutes, turning the meatballs halfway through, until they are firm and have a crispy exterior.

Serve the vegan meatballs with your favorite marinara sauce and pasta, or enjoy them in a meatball sub sandwich.