When I first started I got in trouble with the cutting as well as the 1/4" seam. Check you strips. Did you use the ruler or cutting mat as a guide? Which side of the line did you use? I didn't know it would make a difference when I first started. Also the pressing of the fabric can make a big difference. It's good you are doing a rail fence first. Keep going, it will look good when finished and you can work on making them more accurate as you go along. If you have to piece the backing, you could easily use up the ones that are too small on the back.