OBOs are an amazingly fun way to serve oranges. I'm pretty sure this same technique would work with grapefruit and could be awesome with a cherry in the middle.
Toothpicks can be used to eat the segments with because food is just more fun to eat with toothpicks.
To make OBOs, you will need:
-one or more oranges
Cut the orange in half. If the "navel" parts of the orange are like the north and south poles of Earth then you want to cut on the equator.
Flip an orange half over so that the fleshy, juicy, and delicious part is on your cutting surface. Now cut off the "navel" part so that you can remove the lid and have some of the flesh, juicy, and delicious part exposed.
Next you want to remove the fleshy, juicy, and delicious part of the orange from the pithy, rind part.
To do this, stick your knife into the orange. You should be able to feel where the knife cuts easier on the flesh part. Your knife should be angled but the orange will tell you where to cut. Follow this path of least resistance all the way around the orange.
Liberate the fleshy part of the orange from it's pithy rind prison. Place the orange on your cutting surface with the larger base on the bottom. Cut the orange into segments, I like to cut into sixths for larger oranges and quarters for small ones.
Grab the orange flesh's former pithy rind prison and position it with the larger base up. Place the "navel" end that you cut off earlier into it to create a bowl. This also helps give the orange flesh a higher platform when put back into the bowl.
With the larger base on the bottom, place the orange flesh into the bowl. Add toothpicks in some or all of the segments if desired.
Enjoy your OBO!