Jeanne S

Here is what I do: I cut my fabric into one yard lengths--longer is harder to work with. I use spray starch and iron it smooth. Then fold it in half with selveges together, and hold it out in front of me with the fold hanging down toward the floor. I slide the two selveges edges back and forth, looking at the fold until the fabric hangs down smooth without a ripple at the fold. Then lay the fabric flat on my cutting board, with the selveges away from me and the fold toward me. I pick up the fold and fold it up to line up even with the selvege edges, so I will be cutting through 4 layers of fabric. Use the lines on the cutting mat to trim the left edge off, otherwise known as 'squaring up'. Then I use my 24" ruler, placing it on the left side of the fabric, the newly trimmed side, and slide the ruler over the fabric until 2 1/2" of the fabric is underneath the clear ruler, lining up both vertical and horizontal fabric edges to lines on the ruler. Use a rotary cutter to cut the fabric on the right side of the ruler.
If I don't take the time to iron the fabric and get the fold straight, I get bows in my strips---this is a common problem. A wrinkle in the fabric will also give you a weird jagged edge. Also make sure your cutting board is on a hard flat surface, if it bends when you are cutting, you will get bows too.