You can build back-to back x by purchasing two separate seats that have a flat back. Then, place the two backs opposite one another and then find a way of connecting them. Cover the seats with a cover to hide the tie. A high-strength adhesive can be used to connect the backs of the two seats.But why make it harder when there is an easier way! Instead of building a seat by yourself, I recommend that you purchase a back to-to-back model. You will be able to save a lot time and work while still getting the highest quality. These seats can be purchased without having to spend a fortune if you're able to find them.