Making bias binding from dark fabrics has always been a tricky operation. The Clover white marker leaves a clear visible line on dark fabrics but disappears when the heat of the iron touches it. On a regular ironing board, it's difficult to keep the marks intact.
My solution is to use a sleeve board to do the pressing.
The tube of fabric slips over the end of the sleeve board.
Using just the tip of the hot iron, I am able to carefully press the seam open without removing the marks for cutting. In a pinch, this method will also work if you mistakenly draw your lines with a FriXXion marker (ask me how I know...).
Because so many of my quilts have curved outside edges, I make a lot of bias binding and find this method works great every time.
