Preheat oven to 375.
If you're lentils are not cooked, start by cooking them in 2 cups water. Bring to a boil then reduce to simmer for 20 minutes. Cooked lentils are a lot easier.
Saute onion, carrot, and celery with a good pinch of salt for about 5 -7 minutes, until soft.
In a food processor or blender, place walnuts, lentils, oats, breadcrumbs, and all other ingredients, including sauted veggies, and pulse until you get a chunky crumble. Something that resembled ground meat.
In a greased or parchment lined loaf tin, spread mixute. Press down slightly and flatten. Option to spread a tablesppon or 2 of ketchup over the mixture.
Bake for 25 minutes covered, then remove cover and bake for another 5 minutes.