Cut one of the cup sections from the egg carton using your scissors. This will be the base for your nose. If it's too big or wide, trim it down until it's the appropriate size.
Create a papier mache paste by mixing one part water to one part flour.
Cut 1/2-inch-wide strips of newspaper, dip them in the papier mache paste, and affix to the egg carton "nose" layering the strips until you build out the nose to the desired length.
Sculpt the nostrils by adding strips in a rounded, circular manner along the sides of the nose.
Allow this layer of papier mache to dry completely. Repeat the steps above with papier mache, but replace the newspaper strips with plain white computer paper. This is to make it stiff and sturdy and is a lot easier to paint than newsprint, which can crumble and takes many layers. Let the final layer of papier mache dry completely before continuing.
Paint the nose using simple water-based poster paint. For a pinkish flesh tone, mix red and white paint. Allow the paint to dry before continuing.
Cut a piece of elastic long enough to fit your head and add 6 inches for securing and adjustments.
Poke two even holes, using the point of your scissors, through the nostrils. Pull the elastic through and after you've adjusted the length for a comfortable fit around your head, tie the ends in knots, tuck behind the holes and glue to the mask for extra stability.
Complete your mask by adding desired artistic details, such as glitter, freckles or whiskers.