Here is a basic recipe you can start with. The recipe calls for 3 to 4 pounds fish, but it will work with your 5-pound fish.
Roasted Whole Fish
You can use almost any Mediterranean herbs here and vary the flavors. Try branches of rosemary, fresh bay leaves, mint or bunches of cilantro, parsley or basil. For special flavor, roast on a bed of sliced fennel.
1. Heat oven to 500 degrees F. Cut 3 or 4 slashes in each side of 1 red snapper, blackfish or other cleaned whole fish (3 to 4 pounds), rinsed inside and out and patted dry.
2. Rub fish inside and out with 1 tablespoon extra-virgin olive oil. Season inside and out with salt and ground black pepper to taste.
3. Makes sure to get some flavoring into the slashes. Tuck into body cavity 12 sprigs fresh thyme, 16 thin slices lemon and 1 large clove garlic, thinly sliced.
4. Line a shallow roasting pan with aluminum foil (to ease cleanup) and place the fish on a rack in the pan. Roast, undisturbed, until meat is translucent right down to bone, 25 to 35 minutes. Garnish with fresh thyme sprigs. Makes 4 servings.