The night before, pick over beans, cover generously with cold water, and set aside. The next morning, drain water and add fresh water to the beans.
Bring beans to boil. Reduce heat and simmer until just tender-—30—6O minutes.
Drain beans; put in slow cooker on high. Add onion, garlic, bay leaf and chopped bacon. Add maple syrup and enough cold water to cover beans. Stir beans from time to time and add a bit of hot water if necessary to keep the top layer just nicely submerged.
Mid-afternoon, stir in salt and dry mustard. Remove the lid for the last hour of cooking so the beans thicken.