Step 1In a large pot, combine the salt, garlic cloves, bay leaves, allspice, fennel seeds, orange and brown sugar with the water. Heat the water until it comes to a boil and the salt and sugar are dissolved. Remove from heat and set aside to cool. Place the chicken in a non-reactive container large enough to hold it and the brine, and pour the brine over. Place the chicken in the refrigerator to brine overnight. Drain the chicken, discarding the brine, before cooking.
Step 1Coarsely chop the olives and garlic in a food processor or by hand, then set aside.
Step 1In a small saucepan, heat the oil and garlic over very low heat for around 45 minutes, stirring occasionally, to infuse the oil with the garlic flavor. Remove from heat and set aside.
Step 1Heat the oven to 250 degrees.
Step 2Prepare the chicken: Trim any excess fat and skin from the chicken. Using a pair of kitchen shears, cut the spine out of the back of the chicken. Open the chicken like a book and lay it flat over a cutting board, skin-side down.
Step 3Spread the stuffing over the inside of the flattened chicken. Place a sheet of foil over the stuffing, gently pressing it along the sides of the chicken; this will hold the stuffing in as the chicken is flipped over.
Step 4Invert a parchment-lined rimmed baking sheet over the chicken. Lift up the cutting board and baking sheet, “sandwiching” the chicken, and carefully flip the chicken over so it is resting on the baking sheet, skin-side up. Place the rosemary and thyme sprigs over the chicken.
Step 5Place the chicken in the oven and slowly cook until it reaches an interior temperature of 155 to 160 degrees when measured with an instant-read thermometer inserted in the deepest part of the thigh. This will take about 2 hours and 30 minutes. Remove the chicken from the oven and increase the oven temperature to 450 degrees. Remove the herbs from the top of the chicken and brush the chicken generously with the garlic oil.
Step 6Place the chicken back in the oven (the oven may not have yet reached 450 degrees, which is fine) and continue to cook until the skin is nicely crisped and lightly browned, 5 to 7 minutes, and the internal temperature is 165 degrees. The last few minutes, drape the Serrano ham over the chicken to crisp.
Step 7Remove from heat, and serve the chicken hot.