About a week ago I posted about the rosebud, which is perfect for piping directly on cookies, petits fours, etc. The half rose is basically the rosebud with an extra petal on either side to bulk it up; in fact, you can make it as large as you want by adding extra petals to the sides. You'll need a Styrofoam block, a flower nail, a parchment paper square for each half rose (these should be cut a little larger, about 2x2"), a non-toxic glue stick, a dusting pouch filled with a 50/50 mix of powdered sugar and cornstarch (you may need to touch your finger to the dusting pouch to tap out any mistakes), a piping bag filled with green icing and fitted with a round #3 tip, and a bag filled with any color icing you like, fitted with a #104 petal tip.
rosebud tutorial; there are lots of photos taken from every angle there, too).
Here's a view from the underside, looking up:
Then, pipe a similar petal from the right side. Start with the tip against the right side of the rosebud, with the wide side of the tip against the bud's base. Pipe a petal up, across, and down to the center of the rosebud. I'm not sure exactly what angle I was holding the tip that caused the right petal to curl over at this extreme angle. It was unintentional, but I kind of like it! Hopefully it's one of those things that can be recreated through practice.