Any suggestions on how to replace the bottom of cabinets?

[Steven Anderson]

In one of the bathrooms of my rental, the floor of the cabinet became wet and ultimately warped.  The rest of the cabinet is in good shape, but I would like to just cut out and replace the floor section.  Any advice on how to cut out the existing warped flooring and what material to replace it with? 

Thank you for your experienced advice.

Steven