Yes, fold in half first. You should now have a piece that is approximately 10 inches wide by the length of your fabric. Using two rulers butted together, to get the 19 inches, mark the spot top and bottom, with chalk or pins. Take away the rulers and gently slide your fabric over so that you will be cutting on your board. Remeasure just to make sure you have the correct amount and cut.
Then, take the piece you have just cut and refold to do the same thing for the 25 inch cut.