Start with a toss extension in the center and have 2 couples holding hands on the outside.  You may want to place and additional spotter to brace the base holding the entire stunt (whose holding the extension for now).

Now have the couples in hands pop to a hitch with the flier standing on their outside leg and hitching with their inside leg.  The base holding the extension will shift their fliers feet to his inside thumbs and open up his hand for the hitches on the inside.

After the hitches have placed their feet comfortable in the open hand, then have their base pop and guide them up so they stand up comfortably on the base in the middle.   The flies will need to wrap their arms around one another (which they need to practice before they go up in the air). 

When ready the outside flier can pull their libs/stretches and half Hi-Vs for the finish.

a toss