The present disclosure describes roll-up coverings of custom length and/or width for architectural openings, and a method of assembling the same. The custom covering includes at least one outer elongate tape, at least one inner elongate tape, and a plurality of slats. The tapes preferably have lengths along central longitudinal axis extending between first ends and second ends of the tapes that are selected to correspond to the custom length of the covering. The slats are preferably transverse to, spaced apart along, and coupled to the tapes at any desired location along the tape lengths to achieve desired spacings of the slats, thereby providing a subassembly of custom length. The slats may have lengths extending between first ends and second ends of the slats, orthogonal to the central axis of the tapes, and selected to provide a custom width of the subassembly.
