Cook Lentils: In a saucepan, combine brown lentils and water; bring to a boil and simmer for 25-30 minutes until tender. Drain any excess liquid to prevent sogginess.

Preheat Oven: Set your oven to 375°F (190°C) and line a loaf pan with parchment paper to prevent sticking.

Sauté Vegetables: In a skillet, heat olive oil over medium heat, add chopped onion, minced garlic, diced carrot, and celery; sauté for 5-7 minutes until the veggies soften and become fragrant.

Prepare Flax Egg: In a small bowl, mix ground flaxseed and water; let it sit for about 5 minutes to thicken and create a paste-like consistency.

Combine Mixture: In a large mixing bowl, gently mash the cooked lentils, then add the sautéed vegetables, rolled oats, breadcrumbs, flax egg, soy sauce, tomato paste, dried thyme, smoked paprika, salt, and pepper. Mix until everything is well incorporated.

Form Loaf: Transfer the lentil mixture into the prepared loaf pan, pressing it down firmly to create an even loaf shape.

Add Glaze: In a separate bowl, whisk together the glaze ingredients—ketchup, maple syrup, and balsamic vinegar—and spread it evenly over the top of the loaf.

Bake: Place the loaf in the preheated oven and bake for 45-50 minutes, removing it once it’s golden brown. Let it cool for 10-15 minutes before slicing for the best texture.