This is the way he does it in the video:
When he starts his ‘slop shuffle’ at 0:45 it is anything but a a shuffle. He is sorting the deck into a red half and a black half right in front of everybody.
At 1:50 the deck is 26 red cards followed by 26 black cards. He flips the last red card around to mark the transition from red to black.
At 2:10 the mark makes her first guess, ‘red’, and he shows her that she was correct.
At 3:00 after the mark takes the deck and accidentally faces a card. It is red.
At 3:15 he says she got one wrong and takes a card from the black pile and shows that it is red. Every face down card on the table is red at this point, but I think he does this to disrupt her after she picked black several time in a row.
At 3:40 we get to the marker card. The rest of the deck is black from here.
At 4:00 her first guess is black and shows that it is correct.
At 4:25 he says one in the red pile and asks her to pick it out. She succeeds because they are all black, and he shows the card.
At 4:45 he starts to reveal. The two piles closest to the camera are actually correct so he just turns them over.
At 4:50 the two remaining piles are reversed. He gathers the cards together and with a bit of sleight of hand he switches the piles, but if you watch closely at this point you can see that the cards he shows first are red but he gathered them up from a pile that was supposed to be black.