2016 prius how to remove rear seat

I think there's a couple of points where a U-shaped hook in the seat cushion pushes into a nylon grommet? You basically need to feel along the edge, find those points, then with a hand on both sides of the point, yank up hard. This parts page might help:

Rear Seat Components for 2016 Toyota Prius | Toyota Parts

FWIW, at the 2016 Prius reveal in Las Vegas, "team PriusChat" managed to yoink up the rear seat, took some pictures of the battery.

 

You may be able to find the information you need in the Accessory Installation Manual for the leather seats sold in Europe (AIM 003 741-2), available on toyota-tech.eu.

Complete procedures are in Toyota’s Repair Manual, available by subscription to techinfo.toyota.com. Under Vehicle Interior: Seat: Rear Seat Assembly, there are illustrations (too many to reproduce here) showing exactly where to lift and how to disengage the hooks, and other details of the removal, disassembly, reassembly, and installation procedures. The Repair Manual also states:

For the seatback assembly bolts, the tightening torque is 36.8 N·m {375 kgf·cm, 27 ft·lbf}. This is printed in a double box, indicating its importance for “Major areas involving basic vehicle performance.”

Be aware that Toyota warns against this in the Owner’s Manual (PDF), writing on pages 42–43:

As shown on page 36, the SRS side airbags and SRS seat cushion airbags are part of the front seat assemblies, and extra covers may interfere with airbag deployment. The original seat covers have been designed and tested to split open in certain ways when the airbags deploy; your aftermarket covers probably weren’t.

 

Mendel was right. You just jank right up at those points, one hand on either side of the U-shaped hook and it comes right off. Here's a picture of what it looks like.