Gently pound the feather's quill, then slice it with a knife. Stick the knife tip into a board, handle up, blade away from you, and steady it with your chin. Pull the quill back and forth across it to smooth and thin it. Cut to length and use a pair of scissors to trim the shape. Make sure you leave a small tab in front and back. About 1/4".
Or buy some premade and cut a small tab in the back.
Use a small bit of fletching glue to coat the under side of the back tab. using artificial sinew or other strong thread, tie a slip knot and wrap around the tab once- aligning the featehr slightly off center perpendicular to the nock. Continue with the other two in the same way, just further wrapping the thread around now instead of more knots. These should be equidistant from the cock feather. Now, starting with the cock featehr, apply some glue to the under side of the tab on the front. Pull it tight with a knife, and slightly offset (helical). Use another slip knot and wrap. COntinue until they're all attached thusly. Then apply a thin bead on the inside of the quill along the shaft, and coat the thread with pine pitch for durability. Putting the shaft under you left arm and using all your fingers to hold the shaft, the thread, and the glue bottle helps. It sounds hard, but after a little practice it becomes rather easy and you'll be able to fletch and arrow perfectly in about ten minutes.