Make a series of accordion folds (our folds are 1 inch), holding the folds in place with your fingers as you work. Finish with both ends of the ribbon facing the same direction. Thread a needle and knot it, leaving a 1-inch tail. Pass the needle and thread through the layers, about 1/4 inch from the selvage edge.
Bring ends of thread together; knot, close to the ribbon. Cut off excess thread. Glue ends of ribbon together, covering the knot. Shift folds so they're evenly spaced.
Press the center of the bow to flatten, rotating the folds in one direction.