The secret to the perfect fitted kitchens fit is to have it completely level. Step one is to mark the front line of you cabinet run on your floor and if there is any floor height variation, find the lowest point. You should then position the cabinet that is in the lowest point; to make the front level, some sanding may be necessary to one or both front legs.
Just behind the legs the cabinet sides are cut away to make scribing a simple task, the front skirting is also removable.   Next, the sides and back can be made level by adjusting the counter rotational stainless steel back feet. Once you are entirely happy that you have a level surface you can work outwards from this point and secure each cabinet in place through the back foot plates.