Heat the oven to 375°F. With a carving fork or thin long knife, carefully poke the squash through the skin to the center in a couple places. Put them on a rimmed baking sheet and roast, turning once or twice, until the skin darkens in places and the squash collapses, 30 to 45 minutes, depending on the size of the squash or squashes. It should be tender all over when you test it with a knife.
When the squash is cool enough to handle, cut a lid off the top to remove the stem. To keep the strands as long and intact as possible, peel and scoop out the flesh in larger pieces; gently break into the inside to spoon out the seeds and their pulp and separate them from the edible parts of the squash. (At this point you can refrigerate the squash in an airtight container for up to a couple days before proceeding.)
To make the chile crisp, put the Szechuan peppercorns in a small heatproof bowl and press with the back of a spoon to break them up. Add red pepper flakes or chiles and sprinkle with salt and pepper.
Put the oil in a large skillet (preferably cast iron or non-stick) over medium heat. When it’s hot, add the garlic and cook, stirring frequently, until the bits puff and turn golden, about 3 minutes. Pour the hot oil and garlic over the spice mixture in the bowl. Scrape any garlic out of the pan but leave a thin film of oil behind.
Return the skillet to medium-high heat. Add the squash in big tangles of strands, pressing down with a spatula. Cook undisturbed until crisp and browned in places, about 3 minutes, then turn with a spatula to cook the other sides. Serve right away, drizzled with some Szechuan chile crisp. (Refrigerate any remaining chile crisp in an airtight container; it will keep about a week.)