Can’t contribute much else.
Handwriting is the sane way. People’s handwriting typically leans forward, as in italics, or is reserved and leans backward. Forward leaning handwriting leans the direction of a forward slash, or fractions as @JLeslie points out. Forward handwriting is atypical of enthusiastic, zealous, outgoing people.
Backslash is reserved, back-leaning handwriting. and atypical of people who are shy and hold back.
Excellent question. I think people with learning disabilities, like I have, who sometimes wrote things backward in their earliest school years, have more difficulty making the distinction, as I often do.