data merge block ~ ~ ~ {Lock:"Chest Key"}. Steps for making a locked chest in Minecraft 1.21.2 or above version The Minecraft 1.21.2 update added components that brought changes to certain commands.

Uploading a couple of images to the Minecraft Subreddit recently, user rdditar has been able to craft an accurately built singular chest with the look and proportions very similar to the one in-game.