Avoid ever writing "design" as a phase in the product development timeline. This makes everyone involved (including the designers) think design can be delayed, turned on and off, and added on later. But design starts from the moment you have identified an unmet need in the market and decide to address it. Design exists in your intention to solve the problem; it exists in your efforts to put together a team; and it exists in the team's motivation to succeed. Finally, it materializes in the final product that you deliver to your customers.
Design is a tool bag—and a good tool bag is one that organizes well. It helps you orient your vision, assets, and talents efficiently; it reduces the mental clutter that distracts from the job at hand; and it makes "resetting" easy so that the next time you pull the tool bag out, it's ready to go.