With a slab pour, the easiest thing is to have the trench drain be on the far side of the shower from the entry and then work the wet concrete to be your preslope. I'd want enough rebar and fiber reinforcement in that concrete to avoid any future cracking of the slab. Then just use a topically applied membrane like Redguard and tile over it.

Insulating UNDER and around the slab will be critical to the success of this with your home. A concrete slab has six sides, and all of them will lose heat to the surrounding ground or air if given the chance. Then you are paying to heat the outdoors, not your house, and it becomes a money suck to do that. Be SURE that your contractor actually understands that and plans the insulation accordingly.

When doing what GreenDesign recommends, I'll alter it a bit. When the slab is poured, I'll have them box out the area where the shower footprint is, say 3-4" deep, or as deep as needed.

Then when it's time to build the shower, I'll create the floor pitch by packing sloped mud into the boxed out area.

Thanks. That's probably a detail the tile and concrete guys would have to negotiate with the GC (which may be me) before the pouring starts.

Insulation is not going to be an issue. The ICFs create a concrete box of a house with no air gaps, covered with foam insulation ... ready to finish off with stucco or siding. Floors have foam underneath.

Both floor slab methods create a non-cracking slab with lots of remesh and rebar. ICFs floor forms interlock the slab rebar with the ICF wall rebar and fill the whole thing with concrete. It's like a WWI pillbox.

I've done a few ICFs in my day. Good choice. My kids always wanted to come with me to work with the "big lego blocks". lol

We've been watching the build here - it's what decided us on the ACF.

http://ana-white.com/2011/08/momplex

Although her use of child labor is excessive. That poor exploited child has been toting block, making J-bolts, cleaning up the site, trimming foam, and making PR videos.