Combine oats, milk, Greek yogurt, chia seeds, flaxseed, maple syrup, vanilla, cinnamon, and salt.
Divide evenly between 4 jars.
Stir together the nut butter, maple syrup, and cinnamon.
Add a spoonful to each jar and lightly swirl it into the oats.
Mix Greek yogurt, maple syrup, and vanilla for the icing.
Spoon over each jar.
Cover and refrigerate overnight.