Mistress Lena wanted her slave to learn a lesson because she felt like he was doing things deliberately because she had not punished him for any of his mistakes. The mistress used her boots to trample him and also to humiliate him. He had to learn that she would not tolerate any of his nonsense and the pain and humiliation he felt as she trampled and made him lick and smell her boots and feet was enough to get the message home.