Place the rolled oats, chia seeds, and sea salt in a 16-ounce glass mason jar or similar sealable container.
Add the chilled coffee, almond milk, maple syrup, and vanilla extract to the dry ingredients.
Stir the mixture vigorously with a spoon or secure the lid and shake the jar until all ingredients are fully incorporated.
Seal the container and place it in the refrigerator for a minimum of 4 hours, ideally overnight for 8 hours, to allow the oats to hydrate and the chia seeds to gel.
Before serving, remove the lid and stir the oats thoroughly; if the consistency is too thick, add a splash of milk to reach the desired texture.