Drain and rinse your oats and transfer them to a high powered blender, along with the water and maple syrup. Blend on high speed until smooth, without over processing. Over processed oat milk tends to get "slimy".
Strain your milk 2-3 times in a fine metal strainer or use a cheesecloth. Store in the refrigerator in a sealed container for up to 5 days.
Oat milk may separate while sitting the fridge. If so, give it a quick shake or stir before using.