Place raw brats in bottom of crockpot. Then layer (peeled, quartered lengthwise) russet potatoes on top of brats. Then layer bag baby carrots on top of potatoes. Then pour entire jar and liquid from jar of sauerkraut on top of carrots (the jar usually has more liquid, but you can used canned also).
Put the lid on the crockpot and cook for 4 hours. *Important, do not lift the lid during cooking, "you'll break the seal", according to my uncle :)
When ready to eat, you can slighlty mash the potato and carrots with your fork and topped with a little butter if desired, and then eat with brat and sauerkraut. My mouth was watering during the typing of this recipe...enjoy!