Shower tray?

im fitting a quadrant stone resin shower tray this will have no plynth as the depth for the waste is enougth to fit straight onto the floor boards where the waste pipe will run under neath floor level i was thinking of tilling the floor area where the shower tray will sit then bedding it on a 10 mm 5-1 sand and cement mix or ardex s16 would this be okay also im wondering what would be the best way to get acsess to the trap under shower tray as the pipe will be under floor boards and floor tiled any ideas your answers will be more than helpful