You can evaporate carbon onto filmed grids or onto films on slides followed by floating off carbon coated polystyrene films. You can easily remove polystyrene by keeping the grids on a wire net or on a filter paper over the amyl acetate to have clean holey carbon films only. Let me know if you need more details. They're not that expensive, especially if you consider what your time is worth. If the slides are new, it is usually ok to just rinse the slide with a bit of detergent and wiping it dry with lint free tissue.
Place slides in a beaker containing conc.
Rinse with a bit of detergent and wipe dry before dipping into mixture. To get larger holes I presume you would need to add more glycerol to the mixture. The mixture is sonicated for 5 min with a probe sonicator and must be used within a few hours or re-sonicated.