Who or what else would be supposed to make those two ceiling panels float there: David Copperfield the one, and Uri Geller the other? Draw it out, I’m happy to learn.
The elements do not have to rest on all sides. Where possible, they certainly do it, because then, for example, no joint has to be filled. But the things have a standard width of 2.50m and go up to 3m wide. Annoying for rooms that have larger dimensions... then a joint reinforcement is used to connect the elements. Keep in mind, these things are only 5-6cm thick, regularly cast with in-situ concrete over 20cm. That can handle quite a bit. (Here, 55sqm of open space is planned without any beams. No problem according to the structural engineer.)
By the way, the required support is a full 4cm, as I just read from a manufacturer.