If your bullion knots have become squashed out of shape when a garment comes out of the dryer, moisten a cotton swab and wet down the flower petal and mold it into a nice shape.   When it dries, it will stay in place.

If you're having difficulty getting French knots to hold in place in the fabric hole, rather than finishing the knot over the right or left fabric thread, complete the stitch over the fabric thread above or below the start of the knot.  This will hold your knot in a vertical line - especially helpful in aligning and dotting a backstitched "i".