Some time ago I covered a large diaper box with blue flannel. I used hot glue to keep it flat.
I currently have three sets of cloth pieces to use with it: shapes (dozens of shapes cut from pink flannel), story pieces (animals, plants, cars, and more cut from printed fabric), and "It Looked Like Spilt Milk" pieces (cut from white cotton). My sister gave me the idea for the Spilt Milk pieces. It was really easy to look at the pictures in the book by Charles G. Shaw and cut out my own pieces. The kids love hearing the story with pictures that move. I have fun sticking the pictures to the flannel box. The kids also enjoy playing and making up stories with the shapes and story pieces. It's funny to watch how the shapes bag is just as popular as the story pieces bag--either way they are getting math and/or literature exposure!
I love my flannel box.