Slow Cooker Brisket with Onions - Whole30, Paleo

1 *Remove brisket from fridge at least 1 hour prior to cooking. Preheat a large cast-iron skillet or Dutch oven over med-high heat. Liberally season both sides of brisket with salt and pepper. Add 2-3 tbsp avocado oil to Dutch oven and brown brisket until a deep, caramelized crust has formed (approx. 6-7min per side). Transfer browned brisket to the insert of a slow cooker and set aside. **Note: if brisket is larger in size than the pan, slice in half and brown in batches. 
2 Add onions, garlic and a pinch of salt to the pan. Sauté for 2 minutes. Deglaze the pan with ½ cup beef stock. Use a wooden spoon to scrape any brown bits off the bottom of the pan. Add the remaining beef stock and fish sauce and stir.
3 Pour the stock and onions over the brisket in the slow cooker and tuck the bay leaves into the liquid. Cover with a lid and program the slow cooker for 7-8hrs hours on low or 4-5 hours on high. Taste gravy for seasoning and adjust as required.
4 Cook 1-2 days ahead of time and keep brisket in juices until day of serving. When ready to serve, reheat directly in slow cooker. Carve brisket against the grain, transfer to serving platter and spoon gravy overtop.