@ north_beach

What is the nature of your 'virtual set'?
Is the desk overplayed on top of your talent? (Foreground image)
If so, you will have a hard time keying out the desktop to show the hands.
I suspect the studio in your picture is a single image (all background image) and the effect is achieved by replicating the 'virtual set' scenario in the blue screen studio.
That is, the presenter is behind a table that is covered with a table cloth that is the same color as the green/blue screen.

The Virtual Sets included with vMix use the Foreground image of a desk overlayed on the 'Talent' input and so will hide whatever portion of the input they are in front of.


Ice

Yes, this effect can be achieved by having the table as a part of the background layer image rather than the foreground.
So all you need is a) background layer including table and b) foreground layer which is the chroma keyed footage.

@ richardgatarski

"Selling" the 'illusion' is always the biggest challenge with 'Green Screen' work and why VFX Artists go to great lengths to match camera lenses and angles, lighting perspectives and colour correction in the motion picture industry. For this very reason, the television industry is a little more simplistic with it's approach and use of the effect,
[although there are some very cool high-end Augmented Reality technologies out there:
https://vimeo.com/93364476
https://vimeo.com/92926568
]
the majority of uses are limited to 'talent' keyed over a background image, usually the weather report for television, or as you are very familiar with, a sign language interpreter as a corner bug.

The simplest solution to the above 'issue' that north_beach raises is to use a "real" desk in front of your 'talent' that matches or blends well with your 'Virtual Set'.
Failing that, you need to match the relative camera angle of your set with the 'Blue/Green screen' set and have your 'talent' behind a 'mock' desk as in the picture above, then it is just a matter of placing your keyed image of your talent appropriately on the BG image to give the 'illusion' that they are behind the desk in your image (as implied earlier, this is sometimes difficult to 'sell' as the angles and lighting just don't seem right a lot of the time).
Adding a third layer overtop (as vMix does with it's 'Virtual Sets' foreground image) can totally destroy the 'illusion' if you break any of the physical laws associated with the perception of the image, like seeing the hands or papers on the desk, or worse, trying to walk out in front of the desk. When working with such overlays, you have to be very cognizant of what is possible and what is not, otherwise, the image or 'illusion' will lose it's 'magic' and scream to the viewer of it's 'fakeness'.
Using 'Virtual Sets' can be a real boon to production value when used 'creatively' and effectively, but they can also go the other way pretty quickly if the proper care and preparation is not taken in setting them up.


Ice