How to zigzag linen for prewashing

I use to preshrink fabrics before cutting and sewing, but I've always had trouble with linen fabrics which tend to fray in the washing machine even though I've zigzaged the edge. Recently I came up with a better way of zigzaging these tricky fabrics.

Make a single fold about 1‒1.5 cm (½") from the cut edge of the fabric (I eyeball it as I sew), and zigzag the edge down. Doing this takes the strain off the zigzaged edge, so it won't fray at all. This "semi-hem" even seems to alleviate the wrinkly/bunched-up cut edges that often happens from washing.

If you're short on fabric, you can remove the zigzag with a seam ripper when the fabric has dried. I use sewing thread in a pale but contrasting color, so it's easy to see but won't bleed.