Line a baking sheet with parchment paper and spray the tops with a bit of oil. Preheat the oven to 400°F (200°C).
In a medium pot, combine the red lentils with 3 cups of water. Bring to a boil, then cover, reduce the heat to low, and cook for 15–20 minutes, or until the lentils are very soft.
Drain well, let cool, and transfer to a large mixing bowl.
Add the grated potato, carrots, and onion (optional). You can grate them by hand or use a food processor to save time. Add the breadcrumbs, chopped herbs, eggs, olive oil, and spices. Mix everything together until you have a uniform mixture.
With wet hands, form the mixture into patties of your desired size (this recipe makes 12–14).
If the mixture feels too loose, add a little more breadcrumbs or chill it in the fridge for about an hour to help it firm up.
Spray the tops of the patties, then bake for about 20 minutes, or until golden and slightly crispy on the outside, flipping halfway through.