Cover the slow cooker with the lid and set the temperature to low or high, depending on when you want to serve the meat cubes. It takes about three to four hours to cook meat cubes on high, and six to seven hours to cook them on low. Take the beef cubes from the slow cooker when they finish cooking and serve immediately. There's no need to rest the meat when you cook it in a slow cooker. If you made a stew, taste it when it finishes cooking, and adjust the seasonings as needed before serving.