Mark out any pattern information like darts or notches with tailors tacks. Normally I avoid these like the plague but here it is a much safer and more accurate way to include essential pattern info. I usually remove them as I’m sewing so as not to get any of the threads caught in the stitching.
Do Not use iron-on interfacing as the act of pressing and attaching the interfacing will crush the pine on the velvet. Go for sew- in interfacing or silk organza for backing collars.