Build up a subfloor for tub on a concrete slab?

[Modulerics]

I removed a cast iron tub from my first floor bathroom. It's on a slab. The flooring for the tub is actually.down about 2" from the tile in the room. Appears someone may have built up 2" of concrete or mortar and tiled a long time ago. Can I just put my new acrylic tub down in the recessed slot or should I build up some sort of flooring on top of the slab to get it closer to the height of the rest of the flooring?

I'm thinking if I had to build it up to use tapcons for some 2x4s built in a little frame and then a sheet of 1/2" plywood on top of that screwed down. Thayd get it to about the height of the rest of the floor. Then put down my mortar piles and set the tub.

Or just forget it all and put the tub in and use some cove molding of there's a little gap thay caulk couldn't cover. I'm putting back in the LVP flooring that was over the old tile.

 

[Tuttles Revenge]

If the edge is fairly straight or you can make it straight with flooring I would leave it low.

We just did a project where the tubs were sunk about 8 inches below the rest of the bathroom floor.

 

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[Modulerics]

Thanks Tuttles. It's pretty square and the LVP will allow me to make it square as well. Then I'll caulk it