That's where the Mobile Landing Platform comes into play. A new concept led by the USNS Montford Point, the MLP acts as a sort of floating parking lot, allowing larger ships to unload all sorts of trucks and military vehicles, which can then be loaded onto LCACs that are docked in one of three of the MLP's lanes. You can see the LCAC berths on the starboard side bow of the Montford Point, shown above docked with the larger USNS Bob Hope.
While the Montford Point-class has obvious potential in amphibious assaults, it's also being eyed as a huge asset for humanitarian missions and disaster response, acting as a marshaling point for rescue forces.
Take a look at the USNS Montford Point in action in the video below, courtesy of KGTV-10, San Diego's ABC affiliate.