Hi Cathy, sounds like fun for you and for a child's doll wardrobe!! I would find the right sized box and cover it with contact paper. There are so many colors and designs from which to choose now. Or you might prefer to use a small roll of peel and stick wall paper or wall paper border. Any of these might give you the right look on the outside and a complimentary different one on the inside perhaps. Then I would put a dowel rod through it close to the top for hanging the clothes and use the open flaps for the doors to open and close. Hope this helps, Cathy!
Here's a video that might help you - https://www.youtube.com/watch?v=hZYnAJuNBi4
Cathy: here are some good ideas: