patrice,
does that limit the width of that last border? if the final border is, say, 4" or 6", can it work before you add the binding? i can't envision it.
choice #1. you make the sandwich. you leave extra batting and backing all around. you quilt the center. THEN you add a wide border? if you add the border by machine, don't the stitches show on the back? does it matter? do you work it as part of the quilting design?
at the very end you put on the binding as usual.
choice #2. you make the sandwich. you leave extra batting and backing all around. you quilt the center. you add a border, stitching from the back and flipping to the front, as is sometimes done with binding or a wrap-around binding. what is the optimum width for a border using this method? if you then quilt the border, do you quilt through all the layers?
does this method work for smaller quilts only or for all sizes? in the past, i've had to enlarge quilts by adding backing, batting and borders to the original. i used the flip'n'sew method (sort of). the last one was 2-1/2 years ago and i'm still resting up.