Slipping first purl stitch makes LARGE edge loops

I just learned continental knitting at this site, but I can’t seem to get the edges consistent in stockinette. In garter stitch, slipping the first stitch purlwise on each knit row gives the (same) nice edge but I can’t seem to make the transition to stockinette. I am slipping the first stitch (knitwise) on the knit row, which creates a nice edge, but slipping the first stitch (purlwise) on the purl row is ugly – large loops, about twice the size of the first stitch on the knit row! What am I missing?!

Thanks.

When I slip stitches, I always slip the first stitch purlwise and knit the last stitch, regardless of the row I’m on. Another trick is to work the first stitch as normal, and pull and hold the yarn very taut when you work the next couple of stitches. It helps to tighten up the edge without slipping.