Preheat the oven to 450 degrees. Lay the chicken skin-side down and cut straight through the middle of the breastbone, dividing the chicken in half (or ask your butcher to do this). Leave the chicken out at room temperature to dry out the skin and ensure even cooking.
Meanwhile, put all the herbs into a large bowl. Stir in the anchovy paste, capers, and garlic. Add olive oil until the Salsa Verde is loose and flowy. Add the zest of one lemon. Salsa Verde is better when made a few hours or days in advance to allow the flavors to meld. Once made, it will keep in the refrigerator for up to 2 weeks. If it is cold, allow the Salsa Verde to come to room temperature before using.
Using a brush or your hands, rub the chicken with olive oil. Season liberally with sea salt and freshly ground pepper right before cooking. (If you season too early, you will impart flavor but will draw out moisture from the chicken, preventing a crispy skin.)
Slice the zested lemon into thin coins and lay them flat on a roasting pan or rimmed baking sheet. Lay the chicken directly on top of the lemon and roast for about 20 minutes, basting every 5 minutes with the juices. When the meat right by the wing is starting to firm up, pull the pan out of the oven and let it rest for 12 to 15 minutes. When ready to serve, return the chicken to the oven for 3 to 5 minutes to reheat the exterior and re-crisp the skin. Once crispy, remove the chicken from the oven and cut into desired pieces.
Liberally spoon Salsa Verde over the top of the chicken and serve with lemon wedges. (At Ostia, they prefer grilling or searing the lemon before squeezing it over the top. This caramelizes the sugars and releases more juice.)