  Impulsively excited wave trains are of considerable interest in solar coronal
seismology. To our knowledge, however, it remains to examine the
three-dimensional (3D) dispersive propagation of impulsive kink waves in
straight, field-aligned, symmetric, low-beta, slab equilibria that are
structured only in one transverse direction. We offer a study here, starting
with an analysis of linear oblique kink modes from an eigenvalue problem
perspective. Two features are numerically found for continuous and step
structuring alike, one being that the group and phase velocities may lie on
opposite sides of the equilibrium magnetic field ($\vec{B}_0$), and the other
being that the group trajectories extend only to a limited angle from
$\vec{B}_0$. We justify these features by making analytical progress for the
step structuring. More importantly, we demonstrate by a 3D time-dependent
simulation that these features show up in the intricate interference patterns
of kink wave trains that arise from a localized initial perturbation. In a
plane perpendicular to the direction of inhomogeneity, the large-time
slab-guided patterns are confined to a narrow sector about $\vec{B}_0$, with
some wavefronts propagating toward $\vec{B}_0$. We conclude that the phase and
group diagrams lay the necessary framework for understanding the complicated
time-dependent behavior of impulsive waves.
