I used a remnant of upholstery fabric I picked up at the ASG Trading Post several months ago. Gorgeous stuff--it's a tapestry that also has chenille threads. Lots of texture. Basically, all I did was fold it, straighten the two long sides with a ruler and rotary cutter, then round off the corners. No measuring, all improv. Below, you can see my high tech corner template! That little pile of scraps was all that was left over.
I made the runner 2 layers thick. I really didn't have to, but I wanted to use it all, plus I wanted to test my still-new Bernina on something thick and heavy.
I found some olive green faux suede binding while excavating the sewing room and decided to use it. I had originally planned to use slate blue panne velvet binding, but the green was on the table and looked perfect next to the tapestry. I sewed the binding with a 3/8" seam, wrapped it to the back side, and then stitched-in-the-ditch to attach the back edge. Because the faux suede is a knit, I decided not to fold the binding edge under on the back side. I just trimmed the excess close to the stitching. It's not the tidiest finish, but it worked fine. Here's a close-up view: