I must admit, I sounded quite general with what I wrote - naturally each studio has their own system of working; the larger labels are much more likely to have under-designers, not just for the collection shown in fashion month, but for the much more saleable designs presented in the boutiques.
Their job is to lower the hem of the incredibly short and round off the naval-scraping V in a dress, and the like.
Of course at the much smaller labels, often the person who the label is named after will be the person designing the collection and even having a hand in making it (if we're talking
small).
But at other labels the 'designer' is literally just the face of the label - the one that walks out at the end of the show and takes a bow. Though they probably did next to nothing, they are the face that the fashion world recognizes.
Lagerfeld often dreams up (literally) his collections and sketches them, and that is why most of his designs are very flat - it's impossible to imagine exactly how fabric will react when you drape it on a mannequin, and that's why I think he probably has a lot to do with the design of his collections (most notably couture).
style.it
left: Lagerfeld's sketch looks as if it were designed by draping fabric on the mannequin, but in fact it could easily have been flat-pattern cut, even though, ironically, for Chanel couture everything is draped by an atelier anyway (to get the perfect fit).
right: McQueen would have created this design by initially draping fabric on a mannequin to create these shapes - there is no way one can design the fall of the fabric of those sleeves without physically manipulating fabric.
To get back to the point:
Lagerfeld and other such flat designers would take however long to come up with his sketches, pass them to the atelier who would decipher them and flat-pattern cut them using a block; very simple, very ready-to-wear.
McQueen and others such as Galliano and Vivienne Westwood, personally would experiment continually with draping fabric on a stand until they created something they liked - this would then be deciphered by a pattern cutter, meticulously marking on the fabric on the mannequin where seams, tucks and darts would need to be as so when they remove the fabric from the stand, they can see exactly where everything was and create a pattern from it which would then need to be created in example fabric (toiled) and then examined to see if it fit (drape
never fits perfectly first time), then it would need to be edited, fitted, re-toiled, edited, fitted, re-toiled, this can go on countless times before it is right.
Imagine how much time this would take, not to mention how much money it costs in toiling fabric alone. That is why 'drape' is an almost exclusively 'couture' way of designing.. and that is why McQueen and Galliano were heads of couture houses; their hands-on atelier understanding of the habits of fabric is undoubtedly superior to Lagerfeld.