Here is a good place to start, you may need another ruler to get the correct width or if you can use the lines on a cutting mat to line up a straight edge though I do not recommend that, others will say otherwise. In quilting there are a millions ways to achieve the desired affect and you will get lots of opinions. I highly suggest Google and YouTube for finding mehtods that work for you.
https://youtu.be/42w5fuQmqSI
From there you will cut a strip 10.5 inches wide, rotate the strip horizontally and subcut the strip to 15.5. Since the fabric is already folded in half you should end up with 2 10.5 x 15.5 strips provided the fabric is indeed full WOF.
Repeat the same step above for make you next cut for a 10.5 x 9.5, and so forth until you have the necessary amounts.