If you extend the pads on the pcb, then yes, it is possible to hand solder even unexposed pads. Not fun, but if you only want to make one proto, then you can try it. Pretin all the pads on the chip and the board and check to make sure it sits fairly level. Don't try to flow the whole chip and press it down, flat. That will cause bridges. Just level it wherever it wanted to sit on the solder bumps, so you can visually verify the filet on each pad. Reflow one pad at a time with a fine point, because you can't see bridges and messing this up will waste a lot of your time.
If you mess up, you can remove smaller chips by flowing solder all around the sides, thanks to the extended pads and the gap between chip and board. Then clean up with solderwick and try again.
Also beware the pads that don't wrap around the side. Some of them separate from the IC very easily, and that's that. It's as if the pad is just glued onto the outside of the chip with nothing left when it falls off (but maybe just a microscopic bond wire).