Ribozymes with modular architecture constitute an attractive class of structural platforms for design and construction of nucleic acid nanostructures with biological functions. Through modular engineering of the Tetrahymena ribozyme, we have designed unit RNAs (L‐RNAs), assembly of which formed ribozyme‐based closed trimers and closed tetramers. Their catalytic activity was dependent on oligomer formation. In this study, the structural variety of L‐RNA oligomers was extended by tuning their structural elements, yielding closed pentamers and closed hexamers. Their assembly properties were analyzed by electrophoretic mobility shift assay (EMSA) and atomic force microscopy (AFM).