I am knitting a scarf and the outside edges are curling in. The pattern
starts and ends every other row with:
(RS) k1, sl 1 purlwise, k1 or k2. ends with sl 1 purlwise, k1.
(WS) p4, ends with p4.
When I sl 1 purlwise I am keeping the yarn in back because the st before and after this sl st is always a knit stitch. Is this correct?
Should the sides be curling in like they are and then I correct it with blocking or could this be the patterns intended design?
Would it help if I just sl the 1st stitch of every row. (RS) knitwise, (WS) purlwise?
Would this keep the sides from curling?

Slipping only one st doesn't really help keep the edge from curling. Stockinette by itself wants to roll in, blocking will only help a little. You need a few sts of garter or seed st at the edges that will help more, along with a few rows at the start and end. You might try k1 sl k1 sl 1 at the beginning and sl 1, k1 sl 1 k1 at the end to see if that helps, or slip 3 sts, but you need more than one.