Originally published on 5th December 2014 I put the water and veg in on high for 1 hour, and took the gammon out of the fridge, to bring it to room temperature during this time. This is so that you can make sure that it is cooked evenly throughout and that the flavours reach every part of the meat. Around half way through the cooking process, it is a good idea to turn the gammon joint over. Make sure that the ham fits in the cooker and can be covered with the cola. The easiest ever Slow Cooker Ham recipe – A Slow Cooker Gammon joint cooked in apple juice and/or cider with spices for added flavour, smothered in honey, mustard and brown sugar for a delicious outer crunch.. Gammon on carrots, onion and potatoes. Some tips for cooking a gammon joint in your slow cooker. The slow cooker should be preaheated for 5 to 10 minutes and the cola should be heated to simmering point before it is carefully added to the ham in the slow cooker as preheating the liquid will speed up the cooking process. Here are some extremely delicious potato recipes that you can cook in the