The keys to getting pictures like this of just the flower without busy backgrounds are;
1. Pick flowers that do not have clutter within the first foot or so behind the flower.
2. Shoot at less than a foot away from the flower to keep the depth of field coverage shallow but use a high F stop e.g. F22 to get enough depth of field to cover the flower.
3. Shoot at high shutter speeds e.g. 1/250 to 1/500 to reduce the effect of ambient light in the background.
4. Position the strobes so that they light the flower at an angle that does not light the background.