The reason I didn't specify a size for the petal, was in case you did a different size circle. Do you see the stitching line on the side of the circle? That is one half of the petal shape from the line to the circle edge. Take a piece of paper and trace that shape ( whatever size circle you decide to do) fold the paper in half and cut the whole petal. Transfer this to a piece of template plastic or cardboard and make sure to add your seam allowance after tracing the shape.