I got great information for a non slipping ruler from tessagin. Buy a $1 roll of shelf liner and cut it in different widths to place on the fabric under your ruler---NO slipping at all. I place the liner close to the cut edge of the fabric and be out of the way, then cut.
I have some homemade plexiglass squares that I will attach the liner with double stick tape.
Thank you tessagin for the helpful solution.
Jan