Step 1

Finely grind coriander seeds, cumin seeds, peppercorns, paprika, and turmeric in a spice mill. Transfer spice mixture to a small bowl; whisk in garlic, yogurt, and 2 Tbsp. oil. Generously season chicken with salt, then smear yogurt mixture all over. Let sit on a rimmed baking sheet at room temperature at least 30 minutes, or chill, uncovered, up to 12 hours. If chilling, let chicken sit at room temperature 30 minutes before roasting.

Step 2

Preheat oven to 425°. Heat remaining 2 Tbsp. oil in a large skillet over medium-high. Place chicken, breast side up, in pan, then nestle shallots, cut side down, and lemon slices around. Season shallots and lemon with salt. Tuck in oregano sprigs and cook, undisturbed, until shallots are starting to brown, about 3 minutes.

Step 3

Pour ½ cup water into pan; transfer skillet to oven, arranging so legs are pointing toward back of oven. Roast until skin has taken on some color, 10–15 minutes. Reduce heat to 325°; continue to roast until chicken is cooked through and tender (an instant-read thermometer inserted into thickest part of breast should register 155°; it will climb to 165° as the chicken rests) and shallots are jammy, 60–70 minutes. Let rest 15 minutes.

Step 4

Transfer chicken to a cutting board and carve as desired. Arrange on a platter; tuck shallots and lemon slices around. Spoon juices in pan over, top with oregano leaves, and sprinkle with sea salt.