Preheat oven to 325°F.
In a saucepot, cover dried chilis in a cup or so of water and simmer to soften, about 30 minutes. Toast coriander, cumin, caraway and fennel seeds in a dry skillet then grind them in a spice mill/grinder. Purée softened peppers in a food processor with 1/2 cup of the cooking liquid, salt, olive oil, garlic and the juice of 1 lemon. Reserve.
Slather chicken halves with half the Harissa sauce. Marinate the chicken overnight.
Heat a cast-iron skillet over medium-high heat with 2 tablespoons olive oil, 2 turns of the pan. Shake excess marinade off the chicken and place both pieces in the pan skin-side down. Place a second skillet on top of the chicken to weigh it down. Brown chicken 10-12 minutes to crisp skin, flip chicken, add cut lemon to pan and transfer skillet to oven. Roast chicken for 20 minutes to an internal temperature of 165°F.
Serve with extra sauce and top with juice of caramelized lemon, cilantro, almonds and scallions on top.
(For 3 or 4 servings, cook two chickens by transferring 1 to 2 chicken halves to a baking sheet once the skin has browned and roast chicken in the skillet and the chicken on a baking sheet on separate shelves until both reach temperature.)
Harissa will keep about 3 weeks covered in the refrigerator.