You need to explain a process for ensuring the quality of your work. This will come down to a combination of technical skills and aligning all the necessary components of your work. Items you want to touch on in your answer are your organization skills and your methodology or approach to project management, your attention to detail, and the standard you set for your own work.

"I start by reassigning deadlines for myself by bumping them up earlier. I check the quality of my work regularly with consistency. Once I've finished any part of a project, whether the task was great or small, before moving on I proof my work accordingly. Then I go through it again as a whole at the end. If it is written, I'll read it out loud. If it's numbers or dates, I'll use similar systems to check the quality of the work as well. I have several systems for just about any type of work I perform."