Put all of the ingredients into a slow cooker and cook on high for 5 hours.
Spoon the chutney into mason jars along with the remaining sauce/juice.
Store in refrigerator for a few weeks.
Notes
There will be some sauce/juice left at the bottom of the slow cooker. Make sure to store the watermelon rind with the sauce - the rind will continue to soak up the flavor.This chutney will improve in flavor in 1-2 days.I've also made this using a grater attachment (just discard the remaining water) and it has turned out really well.