Remove the lid, tilting it away from you to allow any excess steam to escape. Allow stock to cool slightly. Strain through cheesecloth set over a fine-mesh sieve. Skim off fat if using immediately, or let cool completely (in an ice-water bath, if desired) before transferring to airtight containers. Refrigerate at least 8 hours to allow the fat to accumulate at the top; lift off and discard fat before using or storing stock.