Line the bottom of a 6-quart slow cooker with potatoes and carrots.
Heat ghee or coconut oil in a large skillet over medium high heat.
Season the beef liberally all over with salt and pepper, using more than you think is enough.
Add the beef to the pan and brown on all sides, about 8 minutes. Remove the beef and place in the slow cooker on top of the vegetables.
Lower the heat to medium on the stovetop, and add garlic and tomato paste to the pan and sauté for 30 seconds.
Add broth, tamari sauce (or coconut aminos), apple cider vinegar, and fish sauce into the pan and stir to combine. Pour the liquid into the slow cooker over the beef roast.
Cover and cook on low for 8 hours or on high for 4 hours, until the beef is tender.
Slice the beef thinly. Serve with vegetables and the sauce poured on top.