Preheat your oven to 350°F (175°C).
Arrange the acorn squash halves, cut side facing up, on a baking sheet. Into the hollow of each squash half, place 1/2 tablespoon of butter and 1/2 tablespoon of maple syrup. Brush the exposed flesh with olive oil, then season generously with 3 teaspoons of kosher salt and 1 teaspoon of freshly ground black pepper.
Roast in the oven for 40 to 60 minutes, or until the squash is tender when pierced with a knife; the exact time will depend on the squash’s size.
Transfer the roasted squash to a serving platter. If the halves are too large for individual servings, slice each one in half again through the stem. Lightly drizzle with extra maple syrup and finish with a sprinkle of flaked sea salt. Serve warm.