Peel the pears, leaving the stalks on, and add them to the slow cooker.
Add the cloves to the pears or into the slow cooker.
Add the cinnamon sticks to the slow cooker.
Chop the clementines into quarters and add them along with the spices. You can peel them but it also works if you keep the skins on.
Pour over the mulled wine. (If you have a large slow cooker and the mulled wine doesn't cover the pears you can add apple juice to help cover or an extra bottle of mulled wine).
Put the slow cooker on a hot setting for 1 hour. Then turn it on low for 2 hours and until you're ready to serve. Turn the pears over if the mulled wine doesn't cover them completely. (3 hour cook time in total)
Serve the pears and enjoy the mulled wine.