All aromatic woods should be avoided such as pine, cedar, eucalyptus etc. You can also use plastic sheets in half inch thicknesses for the bottom such as ABS or PVC. You can get them in 4 x 8 foot or 5 x 10 foot sheets. In actuality melamine is a plastic. However it is also used for pressboard covered in it. You can find pure melamine sometimes in smaller pieces sold as cutting boards for the kitchen. Any non aromatic hardwood should also be okay.
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