Try this on a sample. CO a few stitches, knit a couple rows. Then k2, and (k yo k yo k) in the next stitch, k1, (k o k o k) in the next stitch and so on, end with k2. Purl all sts on next row. Then k2 yo, * ssk or skp (for a left leaning dec) k1, k2tog, yo * and repeat to end. Purl back. Next row, k2, * (k o kok) in YO, sl1, k2tog, psso, repeat from * across.
Something like that. Once you get it down (look at the decrease videos) you can experiment with stitch placement to get it to look like that. The first row, might be something different than what I wrote; I can't see the lower edge so not really sure how to start it.