For seed st (seed), K in P sts and P in K sts.
Beginning with K row, for st st, alternate K and P rows.
Cast on even number (70 will make it about 28")
Row 1: (K1, P1) across.
Row 2-4: Work in seed st.
Rows 5-within last 4 rows of completion: Seed 4, st st across to last 4 sts, seed 4.
4th row from end: Seed 4, (K1,P1) across to last 4 sts, Seed 4.
Last 3 rows: Work in seed st.
You may want to make the seed stitching around the edge wider than what the pattern calls for. This is what helps it to lay flat.