That's how I wanted to do it originally but didn't know how and none of the patterns I looked up used that technique.
Every new project that I do gives me valuable new experience so that I don't regret doing this hat. However, I'd be very happy if you could give some more, clearer instructions on this baby hat you saw and possibly a picture so I'd understand what I'm doing.
When I finished casting on I inserted a piece of yarn through that stitches, pulled them tight and meassured them around my head so at least it will fit me.
However, I now had a look at the stitches that way you suggest and it's just right.
Thank you everyone.