It looks a bit tricky when you first look at it, but really it is a little shirring, finish the top like a peasant dress and then bind the legs and add some snaps. I was dubious about shirring the corduroy, but it is so fine that it works really well.
I made a size 74 and it fits Olive perfectly now. I think she is about 67/68cm tall. If I make another pair (and I probably will, I think these are adorable) I will add a little bit of length. There is a pattern for a pinafore/smock in the same Ottobre which has exactly the same top as the overalls, I think I might have to try that sometime too.
The only thing I disliked about it was the nap on the corduroy was going the wrong way in relation to the way the elephants are facing.
Some photos to show you that Cross Olive is occasionally happy.