Fresh is an adjective that describes the state of the herbs (a noun), so the proper phrase would be fresh herbs. If you want to describe how recently the herbs were dried, you would use freshly, an adverb that describes the verb dried. Freshly dried herbs is grammatically correct in that case. Hope this helps!!

It sounds just right to me. You will probably need to explain the concept as it's a very uncommon thing! ahahahah! You could also say "freshly dried fresh herbs". But once again most people will ask you to explain the idea a bit deeper. Over all, keep in mind there might be a very technical way of saying it, but it is not a common saying.

Yes, it is 100% correct to say "freshly dried herbs" - certainly in British English anyway. In this case, "freshly" means something like "very recently", and has nothing to do with the herbs themselves being "fresh". In the same way, we can refer to "freshly cut grass" or even a "freshly inflicted wound". A dictionary example is "freshly made sandwiches".