Place a rack in upper third of the oven and preheat to 425°. Halve squash lengthwise and scoop out the seeds with a large spoon. Using a peeler, remove skin and white flesh. Rub squash with oil and season with salt and pepper. Roast in a baking dish until beginning to soften (a paring knife should easily slip in only about ¼"), around 30 minutes.
Meanwhile, bring chili, maple syrup, mustard, garlic, butter, and vinegar to a simmer in a small saucepan over medium-high, until just thick enough to coat a spoon, 6–8 minutes. Keep glaze warm.
Transfer squash to a cutting board and let cool slightly. Using a sharp knife, score rounded sides of squash halves crosswise, going as deep as possible but without cutting all the way through. (It helps to place chopstick on the cutting board alongside the squash to stop from cutting all the way through) Return squash to baking dish, scored sides up, and tuck rosemary and thyme between a few of the slices. Using a pastry brush, brush some glaze generously over the squash, and season with salt and pepper.
Continue to roast, basting with glaze every 10 minutes, until tender and glaze forms a rich brown coating, about 45–60 minutes. Before serving, sprinkle with chopped smoked almonds (optional).
