I built a similiar type shower. First thing is to buy an adjustable drain fixture. You can screw it up or down depending on how much drainage difference you desire. Next you will need to buy the rubber membrane that you will line the bottom of the shower with. It attaches to the drain and you nail it up on the walls to ensure no leakage also do not cut corners instead fold them into the corners. Next use concrete to build your floor in the shower. I used bag mix. Mix it kinda of dry so you can work it to the desired slope. Then lay your glass bricks and tile.