Simple, cheap and pretty tub base design

 Here`s a tub base frame that would not be hard to recreate.

The top (ie. the tub deck) looks like it`s made out of Caesarstone. 
You`d need to get this professionally cut and it will be pricey.

However, to save money, and if you don`t mind the extra maintenance, you
could also make the top edge of the tub box out of wood. Something like this:

You could stain the wood any number of colours. For the light grey painted tub base in the first photo, a dark grey or light grey wood stain would look fantastic. A high gloss

lacquered look would also be nice.

images via: Coastal Living, Charles Luck Stone Center