Soak the Lentils: Put the lentils in a large bowl and cover them with warm water, ensuring the water level is about 1 inch above the lentils. Let them soak while you prepare the other ingredients.
Cook the Leeks: In a Dutch oven or large pot, heat the olive oil over high heat. Add the sliced leeks and stir them occasionally, cooking until their edges turn a deep golden brown, about 5–10 minutes. A few darker, crisped edges are desirable for extra texture. Scoop out half of the cooked leeks, sprinkle them with ¼ teaspoon of salt, and set them aside for garnish.
Sauté Garlic and Spices: Add the minced garlic to the pot with the remaining leeks and cook for about 15 seconds, until fragrant. Stir in the rice and sauté for around 2 minutes. Mix in the cumin, allspice, and cayenne pepper, cooking briefly for 30 seconds to release the spices’ aromas.
Combine Lentils, Rice, and Seasonings: Drain the soaked lentils and add them to the pot. Pour in 4 ¼ cups of water, followed by the remaining 2 teaspoons of salt, the bay leaf, and the cinnamon stick. Bring the mixture to a simmer. Cover the pot and lower the heat, letting it cook gently for 15 minutes.
Add the Spinach: Place the spinach on top of the lentil and rice mixture. Cover the pot again and allow it to cook for an additional 5 minutes, until the rice and lentils are fully cooked and the spinach has wilted. Once done, remove the pot from the heat and let it rest, still covered, for another 5 minutes.
Finish and Serve: Before serving, fluff the lentil and rice mixture lightly. Garnish with the crispy leeks you set aside earlier and, if you’d like, drizzle hot sauce over the top. Serve immediately while warm.