Spray the slow cooker insert with cooking spray. Add all ingredients to the slow cooker and stir to combine. Cook overnight on low for 8 hours.
In the morning, stir oatmeal with a fork to loosen the steel cut oats and make sure everything is fully incorporated. Serve warm with chopped pecans and additional brown sugar and molasses to taste.
Notes
For easier clean-up and to avoid the slight "crusty" residue inside the slow cooker, place all ingredients in a glass bowl that fits into the slow cooker then add enough water to fill the lower half of the slow cooker. Cover and cook on low for 6 to 8 hours.