You need a sketch book, fine tip sharpie pen, and rolling paper (the kind you use to make joints).
Do your normals sigil making. Use the sketchbook to refine your sigil if you do that sort of thing.
Once you've gotten the design, place the rolling paper over it (should be semi transparent) and trace your sigil.
Do whatever you do after. I'm sure there are other applications for this "technique", so be creative.