Once you can see a "front" or a "back" piece taking shape with neckline and hems aligned, place your Press N Seal. I overlapped beyond the fold and also needed to add a 2nd piece of Press N Seal to account for the bell shaped / flared hemline.
Below, you can see the pinned side seams and the edge of the first piece of Press N Seal.
I always mark the seam allowances exactly as finished, then will measure & transfer those to the pattern. Sometimes I do that when tracing the original piece, other times I do it later.
Here's the body of the pattern cut out of a deliciously lovely tie-dye rayon knit that Marcy & Katherine Tilton sold at Sew Expo a few years ago. The knit stripe is also from them, though it's a little heavier single cotton knit.