This is a perfect way to get more mileage out of your old jeans. There are many different ways to reuse your old jeans, but pieces get ignored, especially the seams. This takes care of that area of the jean that few others bother with.
It really is quite simple too- take glue and your old jean seams and coil it around until you've got a coaster about 3 inches wide. Jeans are cotton, absorbent, and don't stain very easily, that's why we wear them and that is why they make the perfect material for a coaster.