I was going to name the post "Why 6?" but decided there was too much for one post. So, "Why 6?" will have to wait until next week.
Here are the last 2 rnds for the Irish Crochet Rose (from the American Thread Company booklet):
"5th Row. * Ch 7, sc in back of work between next 2 petals, repeat from * all around.
"6th Row. In each loop work 1 sc, 1 sdc, 7 dc, 1 sdc, 1 sc. Sl st in 1st sc of row and fasten thread."
So, the 5th round is basically a repeat of the 3rd round, and the 6th round is basically a repeat of the 4th round. Again sdc or short double crochet is the same as hdc or half double crochet. Sl st is slip stitch and is done the same way as in the link for the baby blanket edging. The picture shows the slip stitch being made. Note that the hook is placed through the back loop only.
This flower in worsted weight yarn is about 4 1/2" across. The one pictured in the first section for the rose and done in size 10 crochet thread is about 1 3/4" across.
As I was thinking about writing this post, I realized that I hadn't said anything about how to attach the rose. Here are some ideas:
To attach it to a sweater or handbag or scarf: I would use floss like one uses for cross stitch. It comes in many colors. It's thicker than regular thread but not as thick as yarn. I would thread a blunt needle with the floss and tack the flower to the object between the outside petals -- where you would place the sc's if you were to do a round 7.
To make a shawl of flowers: I would lay the flowers out how I wanted them to be in the final product. Where the petals touched, I would sc through the tops (either both top loops, the back loops, or the front loops) of touching dc sts, then chain to the next touching petals. If a chain crossed another chain, I would slip stitch them together where they crossed.
To make the flower the center of a square or circle or whatever: I would divide each petal into thirds mentally. For this flower, which has 11 sts per petal, I would sc in the 4th st of the petal, make enough ch sts to start achieving the shape I wanted, sc in the 8th st of the petal, and then ch again, making the next sc in the 4th st of the next petal, etc.
By the way, one isn't limited to just sc, hdc, and dc when making petals. In fact, the booklet has another flower design immediately after this one. (I don't like it as well -- mostly because the petals turn out more square than rounded.) In round 1, one makes only 5 instead of 6 ch loops. It has for our equivalent of Row/Round 2:
"Ch 1, * 1 dc, 7 dc, 1 dc in ch 3, 1 sc in dc, repeat from * all around."
In other words, instead of skipping over the dc's from the previous round and working only in the ch loops, ch 1 -- which counts as a sc in the first dc. Then work 1 dc, 7 tr (triple crochet), 1 dc in the next loop. Finally, work a sc in the dc on the other side of the ch loop.