In a large bowl, combine the yogurt, ginger, cumin, chile flakes and salt. Whisk until smooth and pour into a baking dish. Lay the chicken halves, skin-side up, in the yogurt mixture. Cover with plastic wrap and refrigerate for a couple of hours to marinate.
Preheat a very clean grill to medium. When the grill is hot, brush with the oil.
Remove the chicken from the yogurt, leaving any excess behind, and lay them out on the grill, skin-side down. Cook until the skin is brown and crispy, and then flip. You want to roast them, essentially, on the grill, and avoid "flaming" them or cooking them over too intense heat. That would dry them out. Grill the chicken until an instant-read thermometer inserted into the thigh registers between 155 degrees F and 160 degrees F, 35 to 40 minutes.
Remove the chicken from the grill to a cutting board. Cut into small pieces or serve whole, family style. Transfer to a serving platter and sprinkle with lemon juice. Top with some of the Harissa and serve immediately.
Preheat the oven to 350 degrees F.
In a small bowl, combine the coriander seeds, cumin seeds and caraway seeds. Add the spices to a sheet tray and toast in the oven for 1 to 2 minutes; you should faintly detect the scent of the spices. Remove the tray from the oven and set aside to cool. Add the paprika and chile flakes to the spice mix.
Using a mortar and pestle (or, alternatively, a food processor), grind the garlic cloves until they become a paste, and then add the red bell pepper. Season with salt, and then add the spices and the 2 tablespoons of extra-virgin olive oil and blend well. When blended, transfer the harissa to a container and top with some additional olive oil. This will keep for 3 to 6 weeks, covered, in the refrigerator.