Preheat the broiler. Line a broiler pan with foil and lightly brush with olive oil. Put halibut skin-side down, on the prepared pan.
Whisk 2 Tbsp. olive oil, 1 tsp. vinegar, honey, red pepper flakes, and 1 tsp. salt in small bowl. Brush the tops and sides of the fish with glaze.
Broil until golden brown and just cooked through, 4-6 minutes.
Mash the garlic and salt into a paste with the flat side of a knife. Heat 3 tbsp. olive oil and 1 tbsp vinegar, garlic paste, and olives in a saucepan over medium-high heat, until bubbling, about 3 minutes.
Transfer olive mixture to a bowl and add the tomatoes, celery, and mint. Toss to combine and serve with the halibut.