You need to buy these plastic plates with cells. (Sorry I don't know what they are called.) These plates are pretty much like the celled cloth for cross-stitching.
Cut them into the shape that you need for building a 'cube'. (Please note that these in the photos are not for the 'House') - Remember to leave a hole for the tissue~
This is pretty much like cross-stitching. Just follow the cells and keep stitching and filling the cells on each side.
You can have your own designs just by mixing the colors and patterns.
You can try different stitches for the different parts/patterns.
Or you can extend some parts out and make it in a more 3-D style.
Sew up the seperated sides together. Remember to make the bottom plate open-able so that you can put the rolls in from there.
Finally, this is how it looks and works~ :D