The night before, layer Greek yogurt, oats, maple syrup, and nut butter into a mason jar, finishing with a thin oat layer. The jar should be about three-quarters full.
Pour almond milk into the jar so it sits about 1 cm above the top layer of oats.
Add chopped apple, walnuts, hemp hearts, chia seeds, and cinnamon on top.
Put the lid on the jar and refrigerate overnight.
In the morning, shake or stir the jar to mix everything together and enjoy straight from the jar.