Using some Lion Brand Thick & Quick Wool-Ease (which I purchased brand-new at the Humane Society Thrift Store, by the way! $2!) and a J hook, I made a chain in the appropriate length to fit snugly around Aspen's head. Theoretically, you would measure your child's head in advance. I just sort of wrapped the length of chain around her head to see where I should stop. I joined the chain to its beginning with a slip stitch. After the slip stitch, I then created a second chain the same length and joined it to the beginning with a second slip stitch and wove in the tails of the yarn. At that point, it looked like 2 chains of yarn attached at one point, like a figure-8 pattern, if you "unfolded" them.
Next up was the flower. I switched to some cotton Sugar 'N Cream yarn in yellow and an H hook. (Yes, I totally mix yarns while I'm crocheting. There are, of course, occasions when this can be disastrous. In the case of a headband, I am unconcerned.)
To make the flower (I think) I did this:
Ch 3. Join with a slip stitch to form ring.
Round 1. Sc 5 in center. Join with a slip stitch to first sc. Weave in ends of yellow.
Round 2. (Switch to second color. I used Vanna White's Baby Yarn here.) Sc in 1st sc of circle. *Ch 3, sc 1, rep from* 5 times. (There should be a sc in every sc around, with a small ch between each.)
Round 3. *[Sc, hdc, 2 dc, hdc, sc] in each ch 3 sp. Repeat from * 5 times. Join with a sl st to beginning sc.
Round 4. Working behind this row of petals, sc through back of sc of round 2. *Ch 4, sc 1, rep from * 5 times. Join with a sl st to beginning sc.
Round 5. *[Sc, hdc, dc, 2 tr, dc, hdc, sc] in each ch 4 sp. Repeat from * 5 times. Join with a sl st to beginning sc. Leaving a long tail, weave in ends into flower and use tails to weave flower into headband, hiding and tying off as appropriate.
(I totally did not test out this pattern before posting. I was trying to post it from memory. Let me know if it is crazy!)