  Like the twisting control in magic angle twisted bilayer graphenes, the
stacking control is another mechanical approach to manipulate the fundamental
properties of solids, especially the van der Waals materials. We explore the
stacking-induced magnetic frustration and the spiral spin liquid on a
multilayer triangular lattice antiferromagnet where the system is built from
ABC stacking with competing intralayer and interlayers couplings. By combining
the nematic bond theory and the self-consistent Gaussian approximation, we
establish the phase diagram for this ABC-stacked multilayer magnet. It is shown
that, the system supports a wide regime of spiral spin liquid with multiple
degenerate spiral lines in the reciprocal space, separating the low-temperature
spiral order and the high-temperature featureless paramagnet. The transition to
the spiral order from the spiral spin liquid regime is first order. We further
show that the spiral-spin-liquid behavior persists even with small
perturbations such as further neighbor intralayer exchanges. The connection to
the ABC-stacked magnets, the effects of Ising or planar spin anisotropy, and
the outlook on the stacking-engineered quantum magnets are discussed.
