CO 30 st.
Rows 1-5: knit
6-10: k5, (K5,P5)x4, K5
11-15: K5 (P5, K5), K5
Repeat 6-15 to end, last 5 rows are K.

Length: for full scarf: 60 inches before last 5 rows.
For cowl: 18 inches before last 5 rows.
You should try these on for size before you do those final rows, though.
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Returned to this to teach myself buttonholes and found a great Cowl here!
Buttonhole placement calculator is here:
https://www.sewknitlove.co/knitting-buttonhole-calculator/
How to make easy buttonholes:
https://www.lovecrafts.com/en-us/c/article/5-ways-to-knit...