My mother-in-law asked me to make her a key chain a few years ago, so I fiddled around with Bouton d’Or New Bamboo yarn, which I bought on clearance and has now been discontinued.
I used about a 1/4 of the skein.
Cast on as many stitches as you like. I did 14.
Knit in stockinette stitch (one row of knit and one row of purl) for as many rows as you like. Fold the cloth to see if it fits your needs. Once you are satisfied with the length, begin decreases.
Begin decreases one on purl side, one on knit side until you make a triangle.
Bind off. Fold cloth and sew sides using mattress stitch.
Add buttonhole by crocheting a chain (number of chains depends on size of your button) from your last bind off stitch and doubling back to
Sewn on a button.
Attach key chain.