+1 on what Pearly said.
I do all my cork build-ups exactly the same way. The only difference is I use the 1/8" sheet cork, instead of 1/4"; sometimes doubled-up on the belly side. I would add one more detail, and that is, to always make sure that your strokes with the file and/or coarse sanding block are made in the direction towards the glue joint, and not up and away from it. This prevents the cork from chipping and tearing out.
–John