To slow cook a beef joint, the cooking time typically depends on the slow cooker setting used:

• On High, it usually takes about 4 to 6 hours.
• On Low, it takes about 6 to 10 hours , sometimes up to 12 hours for extra tenderness.

For example, a 1.5 kg beef joint cooked on High should be done in around 4-5 hours, or on Low in 6-8 hours. It's good to check tenderness with a fork after about 6 hours on Low to see if it is done yet. The internal temperature for cooked beef should reach around 71°C. Rest the meat for about 30 minutes after cooking before carving. Some recipes suggest searing the joint before slow cooking to improve flavor, but it's optional. In summary:

Setting| Time Range
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High| 4 to 6 hours
Low| 6 to 10 (up to 12) hours

This slow cooking method results in tender, flavorful beef that can be served with gravy made from the cooking juices.