This tends to be the most fun part of a design process for most; where then – based on learnings – pencil meets paper, dry-erase boards get scribbled on, conceptual models are created, interfaces are designed and developed, and people share ideas through various mediums on how to solve known problems and how to build a solution.
The conceptualization, design, and development phases find a home here, under the "Create" umbrella – of course, not all of these phases need to be completed or even kicked-off before taking advantage of the next, testing-oriented phase of the design process; however, that all depends on the state and fidelity of the solution.
This part is highly dynamic based on the requirements of the problem but includes such elements as information architecture, experience strategy, interaction models, front end development, and more, illustrated through such artifacts as varying fidelities of wireframes and UI designs, interactive prototypes, flows, sitemaps, and more.