I don't think it will be a tangled mess if you leave it in the large yardage. Cutting it up will make a bigger mess because you'll have more exposed edges. I would just wash it the way it is but if you're really worried about fraying & tangling, you can pink the cut edges, zig zag or stay-stitch them or put each fabric in it's own lingerie bag before throwing it in the washer.
You might also try just soaking or very gentle wash cycle rather than using a full agitation.