Lady Zora did not like how dirty her slave was. He did not know how to keep anything clean and she did not want to have to clean after him. So she used her muddy shoes to trample him and also to send a message to him that he had to change. And that is how he learned to be clean. He did not want to have to lick her boots and the floor clean like he had been made to do.
Lady Zora could tell that this guy was trying to flirt with her and she knew that he eventually wanted to nail her. But she had other ideas and she played him to have her way. The mistress got him turned on and after she was sure she had good control over him, she made him lick her boots which were muddy and the poor guy had no choice other than to do it.