I use a ruler and ruler foot to sew HST from a square. Place the ruler diagonally across the square and the stitch line will be 1/4" away. Just make a few test pieces to check you are getting the 1/4" seam that you want before you start.
If I'm in a rush, I've been known to use a small cutting ruler against the normal foot. Checking the needle position before I start. There are no issue with the foot jumping onto the ruler if you go steadily.