There are many ways to make and attach a hood. The pattern you link to is good and uses an easy method for doing this. Knit the rectangle, fold so the short edges are together and seam one of the long edges. That makes the back of the hood. Then sew the short edges to the neckline. When you fold the piece over this way, it's more of a square but that's what most children's hoods are.
You don't need to make a neckband for support but you can make one with a size smaller needle if you like the look. Pick up and knit from one front edge around to the back and then on along to the other front edge and knit in k1p1 ribbing or whatever you like for an inch or two and bind off. You can then sew the hood to the inside of the neckband.
I mentioned in the other thread that when you get near the end of the hood, you can cast off most of the sts leaving the center sts to knit for a few rows more to give a pointy tip to the hood. (Do this by casting off about 2/5 of the sts, knitting to the end, turn, cast off 2/5, leaving you the center sts on the needles.) I've never found this necessary since the corner that forms when you fold the hood over and seam one side is point enough but you can do it.