Cut the tops off the garlic heads, place on a large sheet of aluminum foil and drizzle with olive oil. Wrap in aluminum foil and place in slow cooker for 2 hours. Remove roasted garlic and foil from the slow cooker. Squeeze the garlic from the pods and return to slow cooker. Add coconut oil, chopped onions, rosemary and thyme sprigs. Pour in vegetable stock. Cover and cook on high for an additional 4-5 hours.