I received this item a while ago to try out. It's called Paper Pots: the Perfect Patio Planter. It is made of paper yes, but has a coating on the inside which makes it durable and leak proof. It is just a rectangle bag and I wondered how it would stand and be stable. Not to worry, once the soil is in place, the Paper Pot stands flat and stable.
This photo came with the Paper Pot and demonstrates the finished product. You may fold down or cut the top to suit your needs, I chose to fold it down.