Slim is presented as a very opposing character to Curley in the book through his appearance, actions/body language, his history, dialogue etc.
Slim is described as the “prince of the ranch”, which is ironic as if Curley’s father is the boss of the ranch, or in this case the King, then surely Curley should be the prince, however it is else wise. We discover that Curley does not live up to that status.
Slim is more of a prince to the ranchers than the Boss’s son himself. The use of the term prince can also be compared to the use of other words to describe Slim’s character; “majestic, royalty, master…” all these words show that Steinbeck speaks rather highly of Slim, this shows that Slim is a master craftsmen and a majestic character.
Slim's "authority" means that he gets to decide who deserves justice, and who deserves a little leniency. He's good at reading character, saying "I can tell a mean guy from a mile off" (3.28)—and, unlike some other people in the novel, he's not saying that out of ego. It's just true.
When Slim does lie, he lies for the good of the group or to protect the weak. After Lennie crushes Curley's hand, Slim tells Curley what to do: "I think you got your han' caught in a machine. If you don't tell nobody what happened, we ain't going to. But you jus' tell an' try to get this guy canned and we'll tell ever'body, an' then will you get the laugh" (3.259-260).
This is the kind of lie where you tell your friend that you like her new haircut because you don't want to hurt her feelings: the damage has been done, and now you just have to try to smooth it over until the bangs grow back. As unofficial judge and jury of the ranch, Slim gets to decide who's in the right (Lennie) and what the punishment is (not being able to