In a small bowl, whisk together the maple syrup, Dijon mustard, apple cider, minced garlic, thyme, salt, and pepper until smooth.
Place the pork roast in the slow cooker and pour the maple Dijon mixture over the top. Drizzle with the olive oil.
Arrange the Brussels sprouts around the pork so they sit in the sauce.
Cover and cook on low for 6 to 7 hours, until the pork reaches an internal temperature of 145°F and is fork-tender.
Remove the pork, let it rest for 5 minutes, then slice it. Spoon the Brussels sprouts and sauce over the slices before serving.