Here's a second quilt square I knit. I was stuck for days trying to figure out how to do the zigzag stripe. I don't know how to knit it directly in the pattern and wasn't sure if gluing a ribbon would work well. I tried duplicate stitching on the yarn and that failed miserably after only 4 stitches.
So I ended up just knitting a narrow stripe on its own, in 4 pieces, and then weaving it to the square. A bit chunky, but the colors at least looks good. Maybe one day I'll learn how to do it properly.