It is preferred that you place a called tile on the flat part of your rack and not in your rack among your tiles. This will prevent picking up the wrong tile for expous
Window of Opportunity for a Called Tile (Article ID 107)
It is too late for another player to call the previous discard once the next player has discarded.
Called Tile Can be Racked (Article ID 12)
A player can put a called tile in their rack, although the preference is to put it directly on the rack’s flat part.