Duct tape can be used to hold the upper trim in place while the thin set cures as well as the dam trim for the same reason.
Note how the corner trim is arranged and spaced and how 6” X 6” bull nose tile is used on the top of the dam. The bull nose tile eliminates a grout joint in the case of quarter round use in this area. Imagine the user of this shower cleaning that joint inside the shower on a weekly basis.
At this point pre-fit the shower pan reinforcing wire. The proper wire is at least 2” X 2” 16/16 welded wire. Keep the wire well away from the drain, side-walls, and dam. Be sure to used crushed tile or small stone to keep the weep holes open during the mortar bed installation.
Note: The original builder did not use reinforcing wire in the floor mortar bed nor were the weep holes kept open. This contributed greatly in the failure of the shower pan.
Thoroughly mix the “dry pack” mortar using the proper ratios. An admix should be used to water-proof the mortar bed. In this case “anti hydro” was mixed with water, which in turn was mixed with the dry pack mortar. This mixing ratio was according to the Manufacturers specifications.
Suspend the reinforcing wire on mounds of dry pack to a height approximately in the middle of the bed. Methodically pack the mortar into wire and area between the walls and drain.
A wood float of finish trowel will work well. A short 2” X 4” can be used between the walls and drain to keep the mortar on an even plane. Keep the floor mortar approximately ¼” below the drain height to allow tile to be flush with the drain.
At this point, the walls and ceiling as well as the trim were grouted prior to the floor tile being installed. Excess loose grout is easily removed from the mortar bed.
Dry-set the floor tile for fit and cuts around the square drain flange. “Key in” and comb out the thin set mortar.
Set the tile and press firmly into the thin set be. The use of a beating block is not advised here due to the slope. Finish the process until the shower floor is tiled.
Allow the thin set to cure and grout the floor.
Examine these two photos detailing the process of installing the square stainless steel drain flange.