Place the squash, cut sides up, on a sheet pan. Place 1/2 tablespoon butter and 1/2 tablespoon maple syrup in the cavity of each squash. Brush the cut sides with olive oil and sprinkle the squash with 3 teaspoons kosher salt and 1 teaspoon pepper. Roast for 40 to 60 minutes, depending on the size of the squash, until tender when pierced with a small knife.
Place the squash on a serving platter. If the halves are too large for one serving, cut each piece in half through the stem. Drizzle lightly with extra maple syrup, sprinkle with sea salt, and serve hot.