You know, they can also be machine-sewn together just as other pieced blocks are -- right sides together, 1/4" seam, straight stitching. This is easier to do the bigger the hexies are. You do have to adjust and turn corners at intersections, but it's not too hard to do if the pieces are big enough.
I tried whip stitching hexies together years ago and decided it was not for me. For one thing, the repetitive motions required for whip stitching were hard on my hands. For another, I just could not see why so many tiny stitches (which are also visible) would be better than hand sewing the pieces together. I ended up hand piecing small hexies (the way one would hand piece any quilt block) and was much happier with that method, especially after watching a Jinny Beyer video where she demonstrated how she does it.