There is one question in woodworking that has no correct answer. The question? How high should the top of my bench be? Any answer will only be right for certain tasks. Optimize the height for planing and it’s too low for dovetailing. Make it a comfortable height for running a router and you’ll need stilts to put furniture together.
One solution is a set of bench blocks. Mine were cobbled together from plywood about 8 or 9 years ago and I use them all the time. At left I have one stuck to the benchtop behind the board held vertically in my vise. That prevents the board from flopping back and forth and I can saw without bending and making my back hurt.
It’s just a box with one open end. The exact dimensions aren’t important. If you make two or more, make sure they are all the same size. Used in pairs you can elevate an assembly a few inches above the bench.