Each designer works differently
There are people who like to start with a white page and a flat pattern. I prefer to design by draping fabric on a dress form, to see what happens, how it falls and whether it looks good in 3D. For me, the sketch usually comes later, when I already know which proportions I am going for. There are advantages to each method but this one works for me, because I am fundamentally a visual person who needs to see and feel things.
It is not a routine
Now it my creative process always the same? No. It depends on the project and on the concept I am working on. Sometimes the starting idea will be a place I visit (Project “Jardin Francais” was inspired by the gardens at Versailles), sometimes a thought (Project “Racine” came from the remark that nothing is perfect or permanent), sometimes a feeling (Project Reset was all about texture & the tactile experience of touching fabric).