  In nature, active matter, such as worms or dogs, tend to spontaneously form a
stable rotational cluster when they flock to the same food source on an
unregulated and unconfined surface. {In this paper we present an $n$-node
flexible active matter model to study the collective motion due to the flocking
of individual agents on a two-dimensional surface, and confirm that there
exists a spontaneous stable cluster rotation synchronizing with a chirality
produced by the alignment of their bodies under the impetus of the active
force.} A prefactor of 1.86 is obtained for the linear relationship between
normalized angular velocity and chirality. The angular velocity of such a
rotation is found to be dependent on the individual flexibility, the number of
nodes in each individual, and the magnitude of the active force. The
conclusions well explain the spontaneous stable rotation of clusters that
exists in many flexible active matter, like worms or {dogs}, when they flock to
the same single source.
