If you are using deep frames to hold the cut out comb, #33 rubber bands work well (Thanks, Walt for that info). You can preload them on the frame by putting a few on one end. They go from the top bar to the bottom bar.
The process is pretty simple. Cut the comb to the size of your frame. Lay it in the frame, keeping the orientation the same as it was in the original hive. (Comb openings slope slightly upward) Spread the rubber bands and slide down the length of the frame, spacing them out with three or four on each frame.
The bees will cut them out when they have attached the comb to the frame. The bands do lose some of their tension over time, so they don't "pop" the bees too badly. I have often imagined the bees using them sort of like amusement rides

I still use rubber bands on some cutouts, and I like to use them in conjunction with cross wired frames. But I have made some hinged frames that allow me to lay the comb in place and close it up like a book. Do a search on here for "cut out frames" or something like that.