You find yourself singing in the shower only to look down and find yourself standing in a 3-inch puddle... Your first thought is to think there is a fault with the tray or the waste pipe. Not so!
You have a tray with a hole in it and if you check your tray waste you will see it is a large bore, 40mm hose, so why is the water not leaving the tray fast enough? On assembly, the flexible waste hose has not been set to run off to the house waste at a decline. You will need to adjust this and create more of a decline.
Top Tip: Just like with rain water on a road, the steeper the road is the quicker the water flows, it's rather simple really!