I've seen these types of bags everywhere for knitting and I always thought they were really cute, I searched for tutes all over and used a few to come up with this, its actually fairly easy, much more than I thought it would be.
I used some fun fabric from ikea, Ive seen on here before, green with cute white hippos, lined it with some pink cotton, a black 9 inch zipper was all I had here to use and the handle is pink with white polka dot grosgrain ribbon
everything I already had so even more fun, I didn't have to buy anything extra
The most difficult part for me was getting the corner seams even, where you sew the triangles, I had to do it twice, I also would use more stiffer interfacing when I make another, this one is really floppy, I just used what I
here's where I got most of my tips from http://dragoknit.blogspot.com/2007/02/box-bag-tutorial.html
here's some pix