Use any yarn you like and needles to match, you'll need to use a long circular needle, cause you're going to knit a lot of stitches in one round.
Make a gauge swatch and measure your gauge. Use the gauge and calculate how many stitches you'll need to cast on to reach the width of 80 cm (from point A to B).
Cast on that number of stitches!
Round 1 and every round after:
Knit in garter stitches. When you've knit half of your stitches increase one stitch (at point C, see picture).
There are a number of possibilities for increasing (instructions). In my test I made a yarn over increase in every round, witch will result in a row of holes. Another option is to increase two stitches in every other round. Make sure you keep track of where you should increase so that it's really in the middle of every row.
Knit for about 38 cm (from A to E or B to F, see picture). Fasten off.
In my version there's a crocheted border along the upper edges (from E to A to C to B to F).
Finish by attaching a ribbon of some sort at the points E and F (see picture). I have braided ribbons, but you could knit, crochet or use something else…
If you have a problem or a question, feel free to mail me and I'll do my best to help. The adress is at the bottom.