Step 1: Preheat oven to 180C (160C fan-forced).
Step 2: Score pork skin. Rub in half the oil and salt, pressing salt into scored skin. Place pork, skin side down, in a large roasting pan. Bake for 1 1/2 hrs.
Step 3: Turn pork, skin side up. Increase oven temperature to 220C (200C fan-forced). Bake for 45 mins, until skin is crisp. Remove from oven. Rest pork for 10 mins.
Step 4: Meanwhile, heat remaining oil in a frying pan on high heat. Cook fennel and garlic, stirring, for 1-2 mins, until seared. Add 1/4 cup of water, reduce heat to low and simmer, covered, for 3-5 mins, until fennel is tender.
Step 5: Pour stock into a small saucepan. Bring to the boil over high heat. Reduce heat to low and simmer for 10 mins, until reduced and thickened slightly. Remove from heat. Add horseradish cream and stir to combine.
Step 6: Thickly slice pork. Serve with braised fennel and drizzle with horseradish gravy.