Complete all stitching on the front and back of the biscornu, both sides must be the same size (ie 59 by 59 stitches or 75 stitches by 75 stitches).
Count 2-4 rows from all 4 edges of your finished piece, and backstitch a border around the design. Stitch the same backstitch border on the back piece of you biscornu. This creates your sewing edge for assembling the biscornu.
Cut both pieces leaving approximately 1/2" of fabric from the backstitched sewing line on all sides. Fold back all the edges along the sewing line, and press down with your fingers.
Mark the middle of one of the front sides with a pin. Join a corner of the back piece to the middle of the front piece.
Make a knot using 2 (two) strands of embroidery floss the same color as your backstitching line. Start sewing the top and bottom of your biscornu together using a whip-stitch. Do this by taking a stitch under one of the backstitched threads on the front piece, then one on the back piece, and so forth, until you have sewn 6 of the 8 sides. You may wish to take a few extra stitches on the corners for stability (and it adds a decorative touch, too).
Stop stitching when you have completed all but 2 sides, to leave a hole for stuffing.
Stuff the biscornu with Fiberfil.
Finish stitching the final 2 sides, securing your thread with a hidden knot.
Sew the 2 buttons, one in the center of the front and one on the back, passing the needle through the center of the biscornu to stitch both buttons on with the same length of thread.
Et Voila! You are finished! Enjoy your handiwork :)