Shown with a cast-on count of 21 stitches.  

• Row 1 (RS): K9, k1 tbl, yo, k1, yo, k1 tbl, k9 (23 sts).
• Rows 2 and 12: P23.
• Row 3: K2tog, [yo, k1, yo, sl1-k2tog-psso] twice, [yo, sl1-k2tog-psso] twice, yo, k1, yo, sl1-k2tog-psso, yo, k1, yo, ssk (21 sts).
• Rows 4, 6, 10, 26, and 28: P21.
• Row 5: K7, k2tog, yo, k3, yo, ssk, k7.
• Row 7: K1, yo, sl1-k2tog-psso, yo, k1, yo, sl1-k2tog-psso, yo, ssk, k1, k2tog, yo, sl1-k2tog-psso, yo, k1, yo, sl1-k2tog-psso, yo, k1 (19 sts).
• Row 8: P19.
• Row 9: K5, k2tog, yo, ssk, yo, (k1, yo, k1) in next st, yo, k2tog, yo, ssk, k5 (21 sts).
• Row 11: K2tog, yo, k1, yo, sl1-k2tog-psso, yo, ssk, k1, yo, k1, (k1, yo, k1) in next st, k1, yo, k1, k2tog, yo, sl1-k2tog-psso, yo, k1, yo, ssk (23 sts).
• Row 13: K3, k2tog, yo, ssk, k2, yo, k2, (k1, yo, k1) in next st, k2, yo, k2, k2tog, yo, ssk, k3 (25 sts).
• Rows 14, 20, 22, and 24: P25.
• Row 15: K1, yo, sl1-k2tog-psso, yo, ssk, k3, yo, k3, (k1, yo, k1) in next st, k3, yo, k3, k2tog, yo, sl1-k2tog-psso, yo, k1 (27 sts).
• Row 16: P27.
• Row 17: K1, k2tog, yo, ssk, k4, yo, k4, (k1, yo, k1) in next st, k4, yo, k4, k2tog, yo, ssk, k1 (29 sts).
• Row 18: P29.
• Row 19: K2tog, yo, ssk, k3, k2tog, yo, ssk, k7, k2tog, yo, ssk, k3, k2tog, yo, ssk (25 sts).
• Row 21: K1 tbl, yo, ssk, k2, k2tog, yo, k1, yo, ssk, k5, k2tog, yo, k1, yo, ssk, k2, k2tog, yo, k1 tbl.
• Row 23: K1 tbl, yo, ssk, k1, k2tog, yo, k3, yo, ssk, k3, k2tog, yo, k3, yo, ssk, k1, k2tog, yo, k1 tbl.
• Row 25: K1 tbl, yo, ssk, k2tog, yo, ssk, k1, k2tog, yo, ssk, k1, k2tog, yo, ssk, k1, k2tog, yo, ssk, k2tog, yo, k1 tbl (21 sts).
• Row 27: K1 tbl, yo, sl1-k2tog-psso, [yo, k1, yo, sl1-k2tog-psso] 4 times, yo, k1 tbl.