In my view it is said in Flanders, it is even very common, but there might be regional variation...Are you right? Well, not really.
"Ik weet al hoe te koken" is not wrong. It's just something we wouldn't say that way. You could find that construction e.g. in a formally written document. And, it could probably also be more common in the Dutch of the Netherlands but here in Belgium, you'd probably not hear it.