Slip stitches at beginning of row

I am knitting a long rectangle for a poncho. To give a nice edge pattern calls for slipping first stitch on WS (purl row) WYIF. It doesn’t say anything about the RS rows. Other knitters on RAV making the same pattern have also slipped a st on RS row. Do I slip WYIB as if to knit for the RS rows?
Thanks!

Are you doing garter stitch, stockinette, other? Will the edge on the RS row that doesn’t say to slip be seamed? For a seamed edge I would want a stockinette stitch on every row. :shrug: How about a link to the pattern, please.