You've chosen a tedious block. Break it down into units. Make some sample units. I always make my HST units larger than I need and trim down. That seems to help me be more accurate. Starch before and after cutting and sewing. The stitch and flip method is best for me for the flying geese. Again, I make slightly larger and cut down. Even with these "chosen" methods I still have some oops units. Practice on some ugly fabric until you are happy with your work. Also, I am in no way affiliated with this company, but I do love the product! I stumbled on it at a quilt show and have used them ever since. I order them because stores down here don't typically stock them. It is called Stitchin Lines from Marin&Colusa. Web site is marinandcolusa.com. I seemed to have a hard time drawing the diagonal line for sewing. My pen/pencil would drag on the fabric and stretch the block and sometimes not be drawn exactly diagonal. So I use this product. They don't require pencil marking. If you would like samples they will send you some to try. Keep at it. You will get better!