So when you do a French braid in hair, you start off with three small sections. Every time you fold over the outer sections, you incorporate more hair into those sections. This differs from a normal braid, which doesn't increase the size of the three parts of the braid as you go along.
French braiding flesh would require a lot more flesh. Also it wouldn't look nearly as tidy because the other ends of the flesh (those not in the braid) are not attached to anything (i.e. a scalp) so it would be a loose tangled mess.
There's easier ways to make something grotesque and cursed.
Shit, now I'm thinking about it and you'd need something big like a flank steak or a brisket. I don't think a pork-loin would work since it's not broad enough. You'd still need to probably butterfly it, and then fringe the edge so you had strands to work into the braid. Best I can think of would be more like braided filled pastry than anything else. Not a terrible sway to do a stuffed roast or roulade I guess.