Making the Ankle Section
Measure the necessary width of your slipper by starting at one side of your ankle, going under your , and up along the other side of your ankle. Make a note of this as Measurement No. 1. Then measure your ankle by starting at the front and going to the back (don't go around to the front again). Make a note of this as Measurement No. 2.
Your slipper will be knitted by starting at the back of the foot and working toward the toes.
Cast on enough stitches to equal Measurement No. 1. Work in a garter stitch (knitting each row) until the length of your work is equal to Measurement No. 2.
Bind off 16 stitches and knit the rest of the row. Repeat this row once more. You have now bound off the first 16 stitches on both sides of your work and completed the ankle section.
Making the Foot Section
Continue knitting each row until the length of the slipper equals the length of your foot, then knit three more rows so the slipper won't be too tight.
When the slipper is the desired length, decrease the stitches in the last row by knitting one stitch, then knit two stitches together, knit one stitch, then knit two stitches together. Repeat this pattern across the row.
Cut your yarn, leaving a 24-inch length to be used to sew the slipper together. Thread the end of the 24-inch length through the yarn needle, and pass the yarn needle through each stitch along the knitting needle. Slip the stitches off the knitting needle and tighten the yarn, drawing the toe section together.
Fold the slipper in half lengthwise and, using a whip stitch, sew from the toe area along the top of the slipper and up the ankle section. Finish off and cut the yarn. Then sew the seam along the back of the foot. Finish off, cut the yarn and weave all loose ends of yarn into the slipper. Add a pom-pom, if desired, to the top of the slipper in front of the ankle.
Make a second slipper exactly the same as the first.
(credit for this pattern goes to http://www.ehow.com)