Heat oven to 450°F. Line large baking sheet with parchment paper. Halve, seed, and cut squash into 1/4-inch thick slices. Toss with 3 tablespoons olive oil, 1 to 2 teaspoons salt, and chile flakes until evenly coated. Transfer mixture to prepared sheet and roast until tender and slightly colored, anywhere from 15 to 30 minutes, flipping once about 2/3 of the way through. Once tender, cut the flesh from the skin and discard the skin. Leave roasted squash on the tray.