For a ruling, consistency is key
There are two fair options here, shuffle the cards back into the deck and deal a new flop, or select one facedown to be the next burn card.
I dislike the second one as then players have knownledge of what card is out,
I dislike the first one as know players have 4 cards extra they know their opponent does not have.
I always deal three cards face-down and then flip them for the flop but errors can always happen
There are two fair options here, shuffle the cards back into the deck and deal a new flop, or select one facedown to be the next burn card.
I dislike the second one as then players have knownledge of what card is out,
I dislike the first one as know players have 4 cards extra they know their opponent does not have.
I always deal three cards face-down and then flip them for the flop but errors can always happen