Hi NeedHelpPlease.
Mattrebuild is right. The recommendation is to use an electric carving knife if available. To quote DIY Natural Bedding: You could use anything you like, the sharper the blade/finer the teeth, the smoother the cut you will get. You can use a razor blade but don’t be surprised when your cuts are jagged. If you have a knife with a blade longer than the latex is deep you will get a better cut than with a razor blade or box cutter.
Sensei also shared a latex cutting experience here
Ultimately, as long as you aren’t making horizontal cuts to “slit” the foam into a different thickness (which would generally need specialized equipment that you would normally find at a mattress manufacturer, a foam fabricator or supplier, or perhaps a fabric or upholstery store) … it’s not difficult to cut foam to size using an electric knife and all you need is an electric carving knife and a straight edge for a guide and just go carefully and slowly and move the knife in one direction (not a sawing motion). The length of the blade should be longer than the thickness of the layer you are cutting.
Hope this helps you moving forward!
NikkiTMU