Handling "Upside-Down" IC Pinouts on PCB
The 80QFP is thin enough that you may be able to place it upside down on the board, glue it in place, then carefully bend each pin down to its corresponding pad, and solder it. 80 pins is a lot to do that for though, this method is more commonly used on smaller chips.

I'm trying to find a good picture showing this technique.

At least, that's what I would do, just about any other method involving bodge wire (such as gluing it upside down and using wire to bring the pins down to the pads) or adapters will be very cumbersome with a package that size.