I saw a video, I thought by clicking on Gay's link, but now can't find. The link is showing a blank page, now Doing my own search I can't find the one I saw the other day. The one I watched the other day was for continuous binding, where you draw the lines on a square of fabric, offset the lines, seam and cut with scissors along the lines. If you want to make the same size as the sash in a dash, you could use the 2" Binding Tape Maker like this one --
https://www.amazon.com/Kunpeng-BTM50..._df_B077MBRMCQ Then carefully sew down the middle of two of them, much like what LGJARN52 suggested.