As a former Industrial Arts instructor with a Crat industrie specialty there are a number of rugs that can be made with rags. Braided rugs are probably the simplest and you jut stitch the braids together to make the rug. The most common braid is your regulalr three strand braid but there are many variations from ladder braids, to plaits and false braids. the patterns are only limited by your imagination.

Good luck
Charles