The Starbursts are mentioned in both the adult story and the child's story.
Starbursts in the Child's Story
Towards the end of the Child's story, Eight-Point Starbursts emerge from the slits of the Eight-Slit Frond. It is the connecting of the Circle Frond and Eight-Slit Frond via the seams that triggered this process. The starburst is described as being flat:
It is flat like the original discs.
The story describes connectivity between flowers and starbursts:
At a table, Albert drops his Starburst into a Flower where it fits perfectly and slides down. Euclid drops his in next, right on top of the first one. When Carter adds his, the three Starbursts act as one and LOUDLY SNAP APART where the eight points meet. This leaves EIGHT SEPARATE FINGERS that slowly "wake up".
This action appears to cause deafness, much as their attempt to break one of the discs using the crane.
The connection creates what is referred to as an eight-fingered Chorus hand.
Fingers / Hands
The eight fingers prove to be impractical, so the boys manually sever three of the eight fingers from the starbursts.
George ties a quick knot through the Starburst with some FISHING LINE and moves to the band saw where he sets up the Starburst on the platform and prepares to slice off one of its Fingers.
Later, we learn that the two star bursts connected to the flower become hands:
The Flower already has TWO FIVE-FINGERED STARBURSTS in it. ANOTHER is being lowered on the fishing line. It slowly slides in on top of the first two, snaps, and blooms. It looks more like a human hand now. There are still nubs where the three fingers were cut, but they don't get in the way as they move.
Later in the screenplay, the five-fingered hand is shown to have enough dexterity to tie rope knots:
Vaughn ties a rope knot with his left hand and using the Chorus’ Hand as his right. The process is completely organic with the Chorus’ Hand showing all the dexterity of Vaughn’s. Across from him Javier guides him through the steps by tying his own knot. Vaughn’s face shows how serene and even joyful it is to control the Hand now. When he's done he holds the knot up...
Later in the screenplay, Vaugh & Graham remove three fingers from the Mahogany Chorus' hand:
Vaughn and Graham are tearing away THREE DECAYED FINGERS on the Eight-Fingered Hand. The positions of the decaying fingers are the same as the missing ones sliced off the Five-Fingered Hand. The Chorus is conforming to the kids' design.
Moments later, the Mahogany Chorus removes a finger from it's remaining eight-fingered hand:
Just then the Chorus reaches over with its Five-Fingered Hand and pulls off one of the decayed Fingers completely.
Much like the broken flat_disc, the discarded fingers are throw into a hole in the ground.
Using the same trick with the flag (where the kids dumped the Disc fragments last summer), the three LEFTOVER FINGERS are dropped into the deep hole.