In frustrated Ising magnets, classical spin liquids (CSLs) with macroscopic ground-state degeneracy can survive against conventional magnetic order. Here we report the discovery of a high-field route toward spin liquids in a bilayer triangular lattice antiferromagnet, Rb2Co2(SeO3)3. We demonstrate that field-controlled dilution of dimers gives rise to a cascade of candidate CSLs within an intermediate temperature regime. These states are characterized by correlated Ising dimers and are found to exhibit a macroscopic residual entropy of 1/2(1-M/Ms)Rln2, originating from doubly degenerate spin configurations. Owing to the interplay of intra- and inter-layer interactions, these CSLs are stabilized by lattice symmetry breaking, precursory to the low-temperature fractional magnetization plateaus. Such field-induced spin liquids can be understood as a consequence of generalized ice rules. In particular, the 5/6-plateau phase may host a quantum spin liquid ground state. Our results thereby establish a new pathway for exploring diverse spin liquid states across both classical and quantum regimes.