Fist of all, make a sample piece to make your work easier while cutting out the pieces. This sample should be made of something stronger than ordinary paper (I used the cover of the magazine most of the time, I lost the sample pieces like every 2 weeks... :D). Measure out a 10,5x5 cm rectangle, cut it out. There, you have your samle piece. :o)

Now comes loooots of cutting. Take out your magazines, and start drawing the little pieces, with the help of your sample piece.
Try to use as much paper as you can, I could fit 6 little ractangles on a page. Of course you can cut more pages at a time, when I was lazy, I cut like 20 pages up together... :D After that, the rectangles will "mutate" a littlebit, but that doesn't really matter, you'll cut them up anyway.

When you have enough pieces, you can start making the chains. I won't write it down here, it's explained on lot's of sites, like here:
http://candywrapperpurse.blogspot.com
You just don't have to make rings of them.

Make them as long as you want your completed thing to be. Same with the width, make as many chains you want.

After you have your chains, you can start sewing them together.
This is actually my favorite part. :o)
I can't really explain how to sew it together, the site above gives you instructions, but it's really easy to figure out.
You can sew on both sides, but I actually just did one side of the whole thing.

Now you have your big picture. :o)
Now take the big cardboard, and glue your mosaic on it, cut off the parts you don't need.
Now you can get it framed, or hang it up on the wall like this. :o)
I'd love to see if anyone did this, comments are welcome, thanks for looking. :o)