By performing first-principles electronic structure calculations and analyzing effective magnetic model of alkali-doped iron selenides, we show that the materials without iron vacancies should approach a checkerboard phase in which each of the four Fe sites group together in a tetragonal structure. The checkerboard phase is the ground state with a block antiferromagnetic (AFM) order and a small charge density wave order in the absence of superconductivity. Both of them can also coexist with superconductivity. The results can explain the 2×2 ordered patterns and hidden orders observed in various different experiments, clarify the missing link between AFM and superconducting phases, suggest that the block-AFM state is the parent state, and can unify the understanding of various observed phases in alkali-doped iron selenides.