I've made quite a few lately and had bits of various variegated cotton yarns left over so used them and a 5mm needle.
Cast on 42 stitches (or a multiple of 18 plus 6)
Knit 3 rows of garter stitch for the border
Row 4: Knit
Row 5: K 3, P to last 3 stitches K3
Row 6: K3, *(K2 tog) 3 times, (yo, K1) 6 times, (K2 tog) 3 times, rep from * to last 3 sts K3
Row 7: Knit
Repeat Rows 4 - 7, keeping first and last 3 stitches in garter stitch, until piece measures desired length
Knit 3 more rows of garter stitch to make the bottom border
Cast off and darn in ends.