Bill Tindall, E.Tn.
Just like diamond on some substrate, you want the abrasive fixed and that to be ground moving. SiC will not embed in glass. Hence, the glass will be abrading along with the stone or whatever as the two surfaces are slid past one another. Works, but not ideal.

A further disadvantage of glass is its hardness. SiC is easily fractured. Capturing it between two hard surfaces will crush large SiC particles like what is used for flatening (not a significant issue with fine particles).

I don't know what an ideal substrate would be for SiC. A laminate like Formica could be good. Corian might be a good substrate to try.