Glass Splashback - Gas Cooktop

Starting a kitchen renovation. Walls are plaster board and wanting to get a glass splashback behind a gas cooktop. To comply with fire safety do people generally wait until the cabinets are installed and then cut out the 250mm high x length of cooktop of plaster board and replace it with bellis board or similar.

I'd do it before the kitchen is installed, if you do it after you may risk damaging the bench top. Unless its stone, then you can do it before the stone goes on as it takes an extra 5 days for the tops to go on.