A microelectronic device comprises a stack structure comprising a vertically alternating sequence of conductive structures and insulative structures arranged in tiers. The stack structure comprises a first block structure comprising stair step structures spaced from each other by crest regions, the stair step structures each comprising steps defined at horizontal edges of the tiers of the conductive structures and the insulative structures, and a second block structure horizontally neighboring the first block structure and comprising additional stair step structures spaced from one another by additional crest regions, the additional stair step structures horizontally offset from the stair step structures of the first block structure, and a slot structure extending though the stack structure and interposed between the first block structure and the second block structure. Related microelectronic devices, electronic systems, and methods are also described.