The materials: fabric, thread, furniture tacks.
The process: I cut a long piece of fabric into two lengths; I wanted an overlap in the middle, to make accessing the materials underneath easier. I basically just make two large rectangles of fabric with hemmed edges on all sides. Then I tacked it to the edge of the door/table top. I had enough fabric left over to make a simple valance to hang in the dining room, too. The rod and clips came from IKEA. It just requires a simple piece of fabric, no pockets for a curtain rod or anything, since it is literally just clipped to it. Simple! I love that IKEA mentality. Love it.
The cost: I don't remember where I got the giant piece of fabric, but it must have been cheap or I wouldn't have bought it. The tacks were 99 cents, and the curtain rod and clips were under $10 at IKEA. Definitely a worthwhile project. The space is on its way to feeling complete, and I'm eager for that.