You may notice in the video that for the first sl 1-k2tog-psso, I slipped the stitch knitwise, and in the two subsequent repeats, I slipped it purlwise. As you can see from the picture of the sample, there really isn't a difference in appearance based on how the stitch was slipped. Slip the stitch however you prefer for this stitch pattern. Generally, if a pattern does not state which way to slip, you should slip purlwise. When a stitch is slipped purlwise, the stitch doesn't change - meaning the orientation of the stitch remains the same. Slipping knitwise twists the stitch so that the left leg of the stitch is in front of the needle.