Audition the placement/positioning with - Wash Away Wonder Tape, Wash Away Wonder Tape,
Wash Away Wonder Tapevarious brands eg. Collins, Dritz, Prym.
Simple, Easy, Terrific for precision and pattern matching, Ideal for re-positioning, Holds everything in place, No need for nasty pins, fiddly clips or even basting/tacking, Sew through it without gumming up the needle
It's the ideal method for zip insertion and holding things in place exactly where you want them
Zips, pattern matched seams, welts, overlaid pattern pieces (inside corners), hems and great for knit fabrics and anything that shifts around or creeps
I love the stuff, it's so useful for precision work.
Video clip of some examples