This is done with two saris. I would get two that don’t have much border. That way if the borders don’t match or compliment each other then you can hide them pretty easily. But if you happen to get two saris with matching borders you might like to show them off. Also a lighter weight fabric is better for the top as it won’t be bunchy after being wound around you so many times.
The skirt part is done like #21 skirt style, but over a net or hoop skirt and starting with the pallu end so it is hidden. Of course if you want to show it you are very welcome to. You can make the skirt as big as you’d like or as small, it just depends on the petticoat you have.
The top part is pinned at the waist and then wrapped as tightly as you can as you move up your torso. In this video I do a halter top but you could do a one shoulder or a strapless too. The length of the tail at the back depends on how long of a sari you start with.
Of course you should wear the appropriate bra and not a couple of tank tops underneath 😛
Have fun, experiment, be creative !