Answer: Outlining phase.
The writing process is often divided in several steps to make it easier to explain and analyze, but there is no one "correct method." However, having some kind of consistent process can help you ensure that your writing is well-thought-out, coherent and free of mistakes.
The thesis statement is the main idea that guides the essay. It usually consists of one sentence that provides a claim or a summary about the essay. Most commonly, this is written during the outlining phase. After you have brainstormed and picked out the elements you will discuss, writing a thesis statement is the next step. Your outline will be structured based on the claim you make in your thesis statement.