Present participle phrase: "Speaking slowly and clearly" is used to describe the way of conversation, increasing the complexity of the sentence and clarity of expression.
Infinitive phrase: "to show respect and patience" is used as a purpose adverbial to indicate the purpose of the action, demonstrating the complexity of the sentence structure.
Relative clause: "that ensures they can understand" uses a relative clause to modify "Speaking slowly and clearly", further detailing the effect of the way of speaking, enhancing the amount of information and complexity of the sentence.