Using a chopstick (preferred) or metal grilling skewer, puncture a hole right through the middle of a styrofoam ball.
Cut a length of ribbon. You'll want it big enough not only for the loop, but for the ribbon through/under the styrofoam ball as well. As an example, if I want a 12" drop (IE: the ball sits 12" below whatever it's being hung from), I'd allow 24" for the loop, 6" for the two ends to pass through the 3" ball, and then another 6" or so for knotting, etc... meaning a 36" length.
Fold the ribbon in half, "good" side out.
If using a chopstick, fold the two edges of ribbon over the end of the chopstick by 2", and push through the styrofoam ball, before knotting them together on the other side.
If using a (sharper, pointier) skewer, knot the two ends of the ribbon together (small, tight knot). Use the skewer to GENTLY push the knot through the styrofoam ball.
Carefully pull the knot out of the other side and knot another time or two - you'll want the knot to hold the ball on securely, and pushing the knot through - rather than un-knotted ribbon - has a tendency to leave a fairly wide hole.
Start affixing flowers to the styrofoam ball. I like to push the ~¼" rubber/plastic nub on the back of the flower into the styrofoam, then secure with a pin. I push the pin through the flower somewhere near(ish) to the center of the flower, but not through the hole in the very center of it.
If you're using larger flowers with the small pieces of stem attached, just push the stems into the styrofoam.
If your flower type has several layers of petals, try to push it through a spot where most of the layers overlap - it'll be more secure that way. On this type of flower, I made sure to catch the pin through part of the plastic center, so that it'll remain on the ball. If I had pinned it just through the petals, there's a good chance that the center would eventually fall out.
Continue attaching flowers over the entire surface of the ball. Be sure to lift petals of an already-affixed flower to be able to place the next flower fairly close to it - you don't want any styrofoam showing between the individual flowers.
Once your ball is completely covered with flowers, attach your decorative accents, if using.
If you would like to attach a decorative bow, tie one in a length of ribbon, then push a pin through it.
Pin the bow to either the very bottom of the pomander (hold it up by the loop to see where the very bottom actually is!), or to the top, near the loop.
Your pomander is complete, and ready to bring some color and visual interest to your celebration! Now... make a bunch more.