And if you don't have a jelly roll, you can cut your own 40 strips, each 2 1/2" wide by the width of the fabric.
Let me calculate this: if you get 50 x 64 and it is 32 strips high (after each 2 1/2" strip gives up 1/2" to seams), by 50" wide.
32 X 50 = 1600 -- Yup, it works!