If you have more fabric than you'll need for these strips and aren't afraid to waste a little...I'd cut out a piece larger than I want and not worry about precise sizes..for example, measure 8 inches from one selvedge and tear it at that point till you get a strip that is about 77 inches long - if you measure along the selvedge to about 77 inches and mark it with a pin you'll know where to stop tearing...then, once you get that piece separate from the main piece of fabric, you can more easily cut it to size...if you're confident enough, tear your piece about 19 inches wide by about 77 then fold it in half and cut the two at the same time to the exact size. would that work for you?