Preheat oven and prepare zucchini: Preheat oven to 400°F. Using a spoon, scrape out and discard centers of zucchini halves, creating a ½-inch-thick shell.
Brush cut sides of zucchini evenly with 1 tablespoon of the oil. Sprinkle evenly with 1 teaspoon of the salt. Transfer to a large rimmed baking sheet lined with aluminum foil.
Make pork mixture: Stir together pork and barbecue sauce in a medium bowl.
Bake zucchini boats: Evenly divide pork mixture among zucchini halves. Bake in preheated oven until zucchini is tender and barbecue sauce is caramelized slightly, 20 to 25 minutes.
Make slaw dressing: Meanwhile, whisk together apple cider vinegar, sugar, mustard, celery seeds, pepper, and remaining 3 tablespoons oil and ½ teaspoon salt in a large bowl until combined.
Add cabbage: Add cabbage, onion, and cilantro to apple cider mixture in bowl. Toss to coat.
Finish zucchini boats: Place zucchini on plates, and top evenly with cabbage mixture.
