There are two reasons I attached the hexagons after making the patchwork base: 1- to make sure each hexagon was perfectly centered in each square. 2- to give me greater flexibility on color placement.

I haven’t had any trouble with the hexies fraying at all. I’ve only washed the table runner a couple of times on gentle after all these years, so it doesn’t get a lot of wear. If this was a quilt that needed frequent washing, I would definitely topstitch all the way around each hexie.