Shown with a cast-on count of 21 stitches.  

• Rows 1 and 3 (WS): Purl.
• Row 2: K1, *yo, k3, sl1-k2tog-psso, k3, yo, k1, repeat from *.
• Row 4: P1, *k1, yo, k2, sl1-k2tog-psso, k2, yo, k1, p1, repeat from *.
• Rows 5 and 7: K1, [p9, k1] twice.
• Row 6: P1, *k2, yo, k1, sl1-k2tog-psso, k1, yo, k2, p1, repeat from *.
• Row 8: P1, *k3, yo, sl1-k2tog-psso, yo, k3, p1, repeat from *.