If it complies with the required clearance to combustibles of the individual components, then you can install your grill island against a surface (for example. Blaze grills require a 16” clearance of open air from the grill back). It should come as no surprise that installing a gas grill up against anything combustible is a terrible idea in all cases. If there will be a structure overhead, you’ll need to follow your local code and regulations on vent hoods (and we can teach you how to buy a vent hood). The owner’s manual will list instructions for each of the individual components included in the island.