How many strips are you sewing together? Do you alternate from which end you are starting to sew the strips together? This is to prevent the strips from bowing. Sew two together in pairs and then start putting the pairs together from the opposite end. If the material is slightly off grai, it should not interfere with what you are doing. Don't be too hard on yourself, if you need a magnifyer to see if your grain is off, you should be fine with that. Can you post a picture, so we can see what you have trouble with?