You can add other spices and seasonings: A ¼ teaspoon of cinnamon and a ⅛ teaspoon of nutmeg are nice additions when using a sweet liquid like apple juice. One envelope of onion soup mix adds more flavor to your ham when combined with a savory liquid like chicken or vegetable broth.
Place the ham and liquid in the slow cooker. Cook one hour on high. This will get the temperature of the slow cooker high enough to thoroughly cook the ham. Turn the slow cooker temperature to low and cook for six to eight hours. The picnic ham is fully cooked when its internal temperature reaches 160 degrees Fahrenheit. Remove the ham from the slow cooker and set it on a platter on the counter. Cover it lightly with aluminum foil. Let the ham rest for 10 minutes. It is now ready to serve.