Preheat the oven to 375°F (190°C). In a food processor, blend lentils, breadcrumbs, flaxseed, garlic powder, onion powder, oregano, salt, and pepper until a sticky dough forms. Shape into 12 small meatballs and place on a baking sheet lined with parchment paper.
Bake the meatballs for 20-25 minutes, flipping halfway through, until firm and golden.
While the meatballs bake, blend all cheese sauce ingredients in a high-speed blender until smooth and creamy. Adjust seasoning to taste.
Warm the marinara sauce in a saucepan. Assemble the subs by spreading marinara on the bread, adding meatballs, and drizzling with cheese sauce.
Garnish with fresh basil and serve immediately.