In a jar or container, combine the rolled oats, flaxseed, cinnamon, salt, and raisins. Stir well to distribute the cinnamon and salt evenly throughout—this ensures you won't get pockets of intense cinnamon flavor. The flaxseed adds a nutty richness, and I like to use whole flaxseed rather than ground because it stays fresher longer and creates a nicer texture.

Pour the milk over the dry mixture from Step 1, then add the maple syrup and vanilla extract. Stir thoroughly until everything is well combined and there are no dry pockets of oats—this helps the oats absorb liquid evenly. The maple syrup dissolves better when stirred in with the milk rather than added later.

Cover the jar and place it in the refrigerator for at least 2-3 hours, though overnight (8-12 hours) is ideal. During this time, the oats absorb the milk and soften to a creamy, pudding-like consistency. I find overnight oats taste best when given the full overnight time—the flavors meld together beautifully and the texture becomes perfectly thick and satisfying.

Remove the jar from the refrigerator and give it a good stir. If the oats are too thick for your preference, add a splash more milk and stir until you reach your desired consistency. Eat straight from the jar or transfer to a bowl, add any toppings you like, and enjoy cold or gently warmed.