This game was developed by Susan Garrett, and it’s one of the most basic lessons in ARF! Training. (use that link to Susan’s website to get an eBook with the complete game)
Check out Jones doing an advanced version of this game (and, after that, a little bonus treat of a young Dawson playing the same game!)
If Jones were to start being very insistent on getting the treat underneath my hand (for example, being “nosey”), I would not move my hand and I wouldn’t say anything at all. He needs to figure out to back off the treat. Once he does that, I would give him the treat (I usually say “take” when I want my dogs to take something from me). It is important not to help your dog by giving them cues, verbal or otherwise. Trust that your dog will figure it out!