working without standard seam allowances
I’ve been reading a lot lately about working without standard seam allowances, or pattern manufacturers who don’t provide them. I’ve worked on a wedding gown where I didn’t use them, and since all the sewing was hand-done, had no problem lining up the seam (stitching) lines. My question is this: when machine sewing pieces that have no standard seam allowances, how does one line up the stitching (seam) lines without the parallel edge of a 5/8″ seam allowance as a guide? This is especially confusing on pieces that don’t meet flatly together (ie:princess seams, sleeve caps). Am I missing something that’s obvious?
Thank you so much!