What type of trem are you trying to block? Floyd rose of standatd Fender style? The block of wood works well for Fender styles trems - I have done it myself. It also doesn't look messy as the trem is blocked off in the body of the guitar - squeeze it behind the tone block and the springs for the trem will keep it in place and make sure the trem doesn't move.
Not sure how blocking a floyd rose trem would work as I have never tried to!