You can make a self-binding blanket from two pieces of fabric. Choose coordinating prints, or pair a contrasting solid for the backing with a novelty print or fabric panel for the front. The larger backing piece creates a self-binding with mitered corners. Select a non-directional fabric for the backing for best results. Self-binding blankets are two layers of fabric with no batting, so use heavier fabrics such as flannel or uncut corduroy to make your blanket warmer.
Cut the fabric for the front five inches smaller in both width and length than the desired finished blanket size. Cut the fabric for the back five inches larger in both width and length than the desired finished blanket size. Mark the center of all four sides on the edges of both pieces of fabric.
Lay the backing right side up on a flat surface. Pin the center mark on one edge of the front fabric to the center mark on one edge of the backing, right sides together. Align the edges of the front and backing fabrics evenly from the center, and pin along the edge. Note that the backing fabric extends beyond the front fabric.
Sew the front to the backing with a 1/4 inch seam, leaving 1/4 inch unsewn at each end of the seam. Pin and sew the remaining three sides, leaving six inches unsewn in the center of the fourth side to turn the blanket right side out.
Fold one corner with the raw edges even to form a triangular point. Place the ruler perpendicular across the folded edge of the fabric, with the edge of the ruler even with the end of the seam, to form a 90-degree angle. Draw a line from the end of the seam to the fold, and sew on the drawn line.
Turn the corner right side out through the opening and check to make sure that the miter lays flat. Remove the stitches, re-draw, and re-sew the corner, if necessary, to get the corner miter perfect. Sew miters on the other three corners.
Trim the excess fabric 1/4 inch from the stitching at each corner. Press the seam allowance on all four sides toward the outer edge of the blanket, but do not press the fold.
Turn your blanket right side out through the opening. Reach inside and poke each corner out square with your finger. Iron the corners and edges of your blanket.
Stitch around the blanket on top of the backing fabric, 1/8 inch from the seam where the backing joins the front, to close the opening and sew the binding in place.
Use sheets or extra-wide fabric to make larger blankets. Sew rickrack or other decorative trim over the seam for added flair, if desired.