  In this work, we study a slave-rotor mean-field theory of an extended Hubbard
model, applicable to transition metal dichalcogenide moir\'e systems, that
captures both the formation of Wigner crystals as well as exotic spin states on
top of these charge backgrounds. Phase diagrams are mapped out for different
choices of long-range Coulomb repulsion strength, reproducing several
experimentally found Wigner crystal states. Assuming unbroken time reversal
symmetry, we find several spin liquid states as well as dimer states at
fractional fillings. While spin dimer states are always found to have the
lowest mean field energy, several spin liquid states are energetically
competitive and may be stabilized by including gauge fluctuations or further
interaction terms. We further discuss possible experimental signatures of these
states pertinent to two-dimensional moir\'e heterostructures.
