One plastic clip per side. Would be much easier if they were metal. Be careful, all the exposed steel is stamp "cut" and has sharp edges. I couldn't wear gloves because I could not feel where the slots were to push the clips.
To get to and push the clips, go between the cushions above the child seat ties, I used a Tums bottle to hold the cushions apart to give a little extra work room. When the clip released (for me anyway) it didn't pop or anything so I just wrestled the seat back until it got loose. Use the second Tums bottle to hold up the first side loosened so it doesn't fall down and relatch (Just in case, so you don't have to open the third bottle of Tums).
The rear seat and hardware weigh in at about 100 pounds, so it is worth it and the floor space revealed is nice too. I remounted the subwoofer to the back wall with my own made brackets to the rear seat bolts and a lengthened harness. I also relocated the jack to the back wall with custom bracketry.