"Well aside from actually hiding cards up your sleeve, which is extremely obvious by the way, don't try it, there's two main ways. On your side, insisting on only one deck and counting cards. But for me, the dealer.."

He deals the cards out again, his hands are quick, not so much because he's robotic but because he's just very practiced at dealing out cards. It's almost imperceptible but he deals her two cards off the top of the deck while his two were from the bottom. If she wasn't looking at his hands it would have been invisible.

"What a stroke of luck to have a ten again." His voice sounds smug about that. Definitely a coincidence. Certainly not that he knew what was on the bottom of the deck. "Did you see what I did there?"