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@vickysteeves if you are going to make multiple of those, definitely get the custom punch.
If it's a one-off, you can press (both?) hard covers between two strips of wood and clamp them tightly. Mark and drill; if you can use one of the pre-perforated sheets for reference, that's best. That should get you a clean cut on each hole.
@federicomena ah I'm in an apartment so maybe I bite the bullet and get the punch...
@vickysteeves around here stationery shops will punch that kind of thing with the machines they have... if it's a one-off, that may be cheaper 😀