Basement Concrete As Shower Floor?
Let me explain what I did once, maybe it will help you.
I was pouring the basement floor of a duplex. The bath rough-ins were back to back. I didn't want to mess with the pre-slope, etc. as I was pouring the 1800 square foot pour, so I formed the two shower areas off separately.
Then I went back months later and established my drain height and poured my pre-slopes. You'll want to use a drain which the rubber membrane clamps into. I brought the rubber membrane up the walls a bit, and up to the surface of the existing concrete.
Then I poured my second pour on top of this and tiled over everything.
You can use the hydro ban as suggested as well. I prefer the rubber membrane because I think there might be some shifting at the wall/floor corner and I wouldn't expect the liquied waterproofer to move as much as the rubber membrane.
You'll notice, I believe, that everyone is pushing you towards a pre-slope and the special drain with weeping holes. I think you'll find that this is a little more work, but it is the correct, most foolproof way to do it. If you just have a standard floor drain with some epoxy coating on the floor and the epoxy coating fails in some area, then you have water in your slab. The membrane system ANTICIPATES leaks and takes them via the second drainage plane into the drain.
One could argue that a standard floor drain on pre-sloped concrete would be fine even without the epoxy. Any water that seeps down into the concrete will just dissipate into the earth, right? The problem with this is keeping it clean and keeping some funky fungi from coming up through the concrete.