On the picture you indicated I counted 29 knit stitches, so k29 and p28 for a total of 67 stitches. Website says #5 or #6 needles. After casting on I'd knit 2 rows of garter stitch then k1, p1 row, etc., and end with 2 rows of garter stitch before binding off.
Yes, slipping the first stitch gives a neat edge.
Please show a photo of your scarf before you go to far so we can see if I gave you proper directions