The shower pan floor is a 3/4" layer of plywood with hydronic heating tubes and mudbed. You can barely see the small square of Ditra I used to close the drain hole slightly to contain the additional mortar bed for the shower pan. I'm using a thinset mortar (slurry) to bond the deck-mud to the substrate.
The mud bed will be at least 1-1/4" thick around the drain, which is normally the weakest section of a mortar bed in a shower-pan. The height of the mud around the drain will dictate the height of the outside perimeter of the mortar bed.
Usually the slope is 1/4" per foot drop. This is sometimes changed to accomodate other factors .... BUT always keep a positive slope to the drain.
After I have my srceed and drain height established .... I set the drain firmly into the mud.
Mortar bed is complete.
Kerdi waterproof membrane has been install on the floor.
Meanwhile ... I installed Ditra to the bench I had build. As you can see, the plumber has installed heating tubes for the hydronic heating system. The Ditra will act the same way to hold the mortar bed over the seat as would poly and lath.
Thinset mortar is applied to the Ditra to fill all the small squares (dovetails) and act as a bond-coat for the mortar bed.
The mortar bed is at least 1-1/4" thick above the height of thr heating tubes.
Kerdi membrane has also been applied to the seat as well as the shower-pan floor.
The next day I installed Kerdi up the walls about 12" or more including the front of the bench and behind.
Next ... I apply a generous coat of liquid waterproof membrane (2 or more coats). Kiesel Okamul DF
It isn't required to come outside the shower, although I brought the waterproofing out over the edge a couple of inches.
It's very important to use the Kiesel fiber-tape in the corners to ensure the is no possible compromise to the waterproof system.
Apply another coat as soon as the tape is set into the fresh coat. (I don't have a photo showing)
Okamul DF may be brushed, rolled or troweled over the surface .... but I personally like to trowel, although I'll use a stiff (cheap) brush for corner applications.
The main area floor consists of 1" hexagons and 1" glass and 1" mosaic for the outside pattern.
There is a similar pattern in the shower-pan floor, without the glass 1" tile.