Divide yogurt, honey, flax seeds, cinnamon, kosher salt, almonds, oats, and milk evenly between two 8–10-ounce glass jars or small glass bowls with tight-fitting lids.
Securely close or cover containers; refrigerate at least 6 hours, or up to 48 hours.
When ready to serve, remove lid, stir, and top with berries or citrus, yogurt, and flax seeds or almonds, if desired.