Lady Karame was pissed off at this guy because he was used to ignoring what he was told. He had to be punished and the mistress did this with her boots. She ensured that he learned his lesson and that he felt as much pain as he could feel. That is why she used her boots to punish him. He had to lick the soles and he had to endure the trampling.
Lady Karame wanted this guy to fear her. He did not and she felt that it was not ok for him not to fear her. She stripped him naked and she used her high heels to scare the shit out of him and to make him fear her the way she wanted. The mistress brutally trampled him and he threatened to crush his nuts and also his dick if he did not do as she said.
Lady Karame had given her slave work that he did not do as she wanted. She was pissed and she had to teach him a lesson. The mistress did not like the fact that the slave was lazy. So she punished him to show him the consequences of being lazy. The mistress got the loser to lick the soles of her boots and was promised some trampling if he did not improve.