The 'Gossip Girl' star knows it is a "lot of work" selecting and organising her own outfits rather than having a team do it for her but she enjoys being creative.
She said: "It’s a lot of work - I mean, it’s not hard in that we all dress ourselves every morning. So once you have the clothes, you just pick out what to wear like any other human being does. But it’s easier because you have access to clothes and so it’s not that hard.
"The hard part is going through all the fashion shows and screenshotting all the looks you like and calling them in. I have an assistant who helps in calling in the looks. But a lot of it is I have relationships with the designers."
And the 30-year-old actress - who has James, three, and 17-month-old Ines, with her husband Ryan Reynolds - likes being able to be in "control".
Speaking to Women's Wear Daily, she added: "Probably because I have control issues and a big ego - that’s probably the honest answer. I just like it. I love design and I love fashion and it’s a way to be creative. In my job I get to be creative, but it’s over a period of time and so many other people are involved, whereas this is a beginning, middle and end, and I get to be creative and there’s an end date in the near future.
"It’s the same reason why I like doing my friends’ hair and makeup or cooking - you get to be creative and finish it. Whereas with my job you do it and then two years later it’s finished. It probably goes back to the control issues; it’s like, 'Ok I did it, I completed it, it’s done!'"