A newly formed high-density lipoprotein particle; consists of a phospholipid bilayer surrounded by two or more APOA1 molecules. The discoidal HDL particle is formed when lipid-free or lipid-poor APOA1 acquires phospholipids and unesterified cholesterol from either cell membranes or triglyceride-rich lipoproteins (undergoing lipolysis by lipoprotein lipase).