Sewing a 1/4" seam is extremely important when piecing blocks. Learn where the guideline for the 1/4" seam is on your sewing machine is. If there is none, make one with tape. Some sewing machines have an adjustable needle position. Use this to help sew your 1/4" seam. Measure your units after you piece and press to make sure they are the right size.
All seams are pressed toward the unit with fewer seams or toward the darker fabric. I have scanned the back of the block to demonstrate this. Click here to see the back of the block