Question: Where do you put a tile after you’ve called it?

Answer:  Once a player has picked up a called tile, the tile should be put on the top (flat part) of their rack and not in the rack (sloped part). This is a new ruling and the penalty for not putting the tile on the top of the rack is currently undetermined. A called (claimed) tile should not be placed on your rack in the sloped part.

Source:  MJME 2024, page 15, paragraph 2 & 31, paragraph, 2