Helen, yes French Flags, that's what they are.
A French Fly is the flat front, of a pair trousers.
I had a bespoke tailor make a pair of kangaroo leather trousers for motorcycle riding about 32 years ago, she aksed me whether I wanted a french fly, a straight zip or a combination of both. I had never heard of that before.
I got the combination and wonder of wonders, I still fit into them and use them still.