I grind all my folder blades by holding the tang between my thumb and index fingers and the fingernail of my other index finger as a tool rest with that thumb applying pressure to the blade against the wheel.
I make two blades at once, back end to back end, so I always have a handle. After grinding the flats and cutting them apart, I mount them in the unfinished handle to finish grind the blade.
I use my Bruce Bump file guide! With a handle welded on to it.. ( from a fixed blade that didn't cooperate. I showed it! ) Holds the blade, as well as sets the plunge lines perfectly.