I am building a new house and now face a question in the master shower/tub area. It's shown below as a roughly 7' by 7'9" with shower at one side and a freestanding tub at the window. Architect told me that what people normally do is to slope the entire floor to the linear drainage on the right side, and have the tub with adjustable legs for leveling. It seems like the tub with legs will have the bottom "open". How does the drainage work in that case?

My contractor only has experience with freestanding tubs with flat bottom (that are somehow fixated to the floor so they don't move). Has anyone have any experience with adjustable leg tubs and how they might work in this situation? How is the drainage sealed? Or, can I make a flat bottom tub work on the slope?