Visually your hierarchy is a pyramid. At the top of the pyramid is your policy recommendation. Your policy recommendation is supported directly by a number of primary supporting contentions. Those, in turn, are supported by secondary supporting contentions. The structure of the pyramid. is up to you. Only you can decide how many primary arguments there are for your policy. Only you can decide how many secondary arguments are required for each primary argument. At the base of your pyramid. you must supply the empirical evidence upon which the whole edifice is built. Textually your hierarchy is an outline. One example might look like this:

• Policy Recommendation (aka "Primary Contention" or "Thesis")
  • Supporting Contention #1
    • Subordinate Supporting Contention #1
      • Evidence for Subordinate Supporting Contention #1
    • Subordinate Supporting Contention #2
      • Evidence for Subordinate Supporting Contention #2
  • Supporting Contention #2
    • Subordinate Supporting Contention #1
      • Evidence for Subordinate Supporting Contention #1
    • Subordinate Supporting Contention #2
      • Evidence for Subordinate Supporting Contention #2
    • Subordinate Supporting Contention #3
      • Evidence for Subordinate Supporting Contention #3
  • Supporting Contention #3
    • Evidence for Supporting Contention #3.

Remember, a contention is a statement of fact for or against a proposal. Your contentions are statements of fact for (on behalf of) your policy recommendation. Since a sentence is the smallest grammatical unit that is capable of making a statement, it follows that your contentions must be sentences. Without supporting empirical evidence your contention is just an assertion. The passion with which you believe something to be true is not evidence for its truth. Show me the evidence! And document the source!

For more about formulating policy recommendations and contentions, please consult Getting from Topic & Bibliography to Recommendation & Contentions.