Dear sewing community,

I am a beginner when it comes to sewing so I’m not sure what went wrong. I did a simple headscarf, basically a square piece of fabric with narrow rolled hems.

I did all four sides the same way, pressed it, pinned it, sewed and pressed again. The fabric is very slightly stretchy in one direction and the stretchy sides turned out nice and flat, while the non-stretchy sides look slightly crumpled despite ironing.

It doesn’t make sense to me, according to my logic it should be the other way around. But anyways, what does one do to prevent that?