If you have a few mates that are into working on cars like i do , borrow an engine crane assemble it in the bathroom.
use some packing strap around the base lifted it and wheeled it into postion and slowly lowered it onto the mortar bed.
A very easy 1 man operation.
didnt bother pulling the packing strap out , i just cut it flush with the top of the pan when the bed is dry.
My ensuite had a hole directly over the shower tray for the fan/light. I secured a block and tackle through the hole and attached same to the tray whilst on a workmate with strong webbing. Took away workmate, laid mortar, lowered tray, cut straps.
I have another to do next month, will do the same. probably best if there is access to room above, but screw hooks into ceiling joists would work.