Place the beans in a large bowl and pick through them, discarding any broken beans or stones. Cover the beans with at least 3 inches of cold water and soak uncovered at room temperature for at least 8 hours or overnight.
Drain soaking liquid from beans, and place beans in a slow Cooker.
Heat a large skillet over medium heat. Add the bacon and saute until it is crispy and golden brown. Remove bacon pieces with slotted spoon and add to the slow cooker.
Pour out about ½ of the bacon fat and place the skillet back over medium heat. Add the onion and saute until soft, about 5 minutes. Add to the slow cooker.
Stir water, ketchup, water, molasses, apple cider vinegar, onion, mustard, and brown sugar into the beans until well mixed and pour over bean mixture.
Cover, and cook on LOW for 6-8 hours, stirring occasionally if possible, though not necessary.
When almost done, add the salt, taste and adjust seasonings.
Recipe by Three Hungry Boys at https://www.threehungryboys.com/2017/03/30/baked-beans/