Combine the salt, vinegar, ginger-garlic paste, and water in a large bowl or container. Submerge the whole chicken completely and refrigerate for 6–12 hours. Once brined, rinse the chicken thoroughly under cold water and pat it completely dry with paper towels. For extra crispy skin, leave the chicken uncovered in the refrigerator for 1–2 hours to air-dry if time allows.
In a small bowl, mix the softened butter with the salt, black pepper, paprika, onion powder, garlic powder, chopped cilantro, and chopped dill until smooth and evenly combined.
Carefully loosen the skin over the breast and thighs without tearing it. Spread most of the herb butter underneath the skin, then rub the remaining butter all over the outside of the chicken to ensure maximum flavour and a beautifully golden finish.
Heat the olive oil in a roasting pan or oven-safe skillet over medium heat. Add the lemon slices, halved garlic bulb, onions, and green chilies, allowing them to lightly char for a few minutes. Pour in the chicken stock, then add the fresh herbs to create a flavourful roasting base.
Place the seasoned chicken on top of the vegetables and roast in a preheated 200°C (400°F) oven for 60–75 minutes, or until the thickest part of the thigh reaches 75°C (165°F) and the juices run clear.
Switch the oven to the broil (grill) setting for the final 10–15 minutes until the skin becomes deeply golden and crispy, watching carefully to prevent burning.
Remove the chicken from the oven and allow it to rest for 10 minutes before carving so the juices redistribute throughout the meat.
Blend the roasted lemons, garlic, onions, herbs, stock, and pan juices until smooth. Simmer the sauce for a few minutes until slightly thickened, then serve generously over the carved roast chicken.