Two layered liquid-liquid inclined flow configuration is commonly found in oil transportation, plastic industries and in several geophysical phenomena. Unlike single phase flow and two-layered horizontal flow, two-layered inclined channel flow can exhibit multiple base states - two in counter-current regime and up-to three in co-current regime. These base states differ from each other by their value of holdups - the location of the liquid-liquid interface from the walls. Layered flows are susceptible to instabilities due to sharp variations in viscosity and/or density. For an inclined two-layered pressure-gravity driven flow, the low Reynolds number interfacial instability crucially depends on the type of base state. The coupling of wall slip with such instabilities in multiphase shear flows has received very less attention in the past. The violation of the classical no-slip boundary condition at the fluid-solid boundary could occur due to a multitude of reasons - microscale flows, surface patterning or flow past porous walls. Here, we investigate the role of wall slip on the multiple holdup states of an inclined two layer flow and probe the subsequent stability characteristics. We identify the faster travelling phase, the one dominating the interfacial interaction leading to the instability. Therefore we have performed the linear stability analysis in two-layered liquid-liquid inclined flow to determine the onset of instability for each base state with different wall slip coefficient β. Linear stability analysis has been performed on the Orr-Sommerfeld equation subject to the interfacial boundary conditions to obtain eigenvalues and eigenfunctions. The stability calculations are performed analytically in the long wave limit (wavelength of the disturbances are asymptotically larger than the transverse dimensions of the channel)and numerically for arbitrary wavelength using Chebyshev spectral collocation method. Neutral stability conditions (when the eigenvalue switches from growing to decaying modes) are obtained as a function of operation parameters like flow rate ratio q. We plotted neutral stability diagrams in both counter-current and co-current regimes in a plane of superficial velocities, considering each solution for different inclination angle θ and channel height H.