An interposer is the name for an interface that links one electrical connection to another. In this repair, it is the board connecting the battery to logic board.
Lift the Interposer off the logic board and remove it.
Removing this board will ensure that the battery remains disconnected throughout your repair, preventing your computer from accidentally powering on. It's also a good idea to take it out so it doesn't fall out unexpectedly.
Use the flat end of a spudger to pry the right side of the I/O board data cable connector up off its socket on the I/O board.
When prying the I/O board data cable connector from its socket, make sure to pry the connector itself and not the socket. Prying the socket may cause irreversible damage to the I/O board.
To avoid scratching the display, open the computer about 90º and set it on end.
Guide the trackpad ribbon cable through the slot cut in the upper case. This will push the trackpad up out of its recess in the top of the upper case. Guide the trackpad out with your other hand, so it doesn't fall.
This can be done without removing the battery. The touchpad ribbon cable can be disconnected on the logic board, then snaked (gently!!) back out its channel with the battery in place.
It won't thread back through when replacing the touchpad though - it's not stiff enough. Instead, cut a strip of material from a manila folder and thread that through the channel under the battery. Then use masking tape to attach the touchpad cable to the manila strip and pull the strip out towards the logic board. The touchpad ribbon threads through the channel and the masking tape can be removed once it's in place.
Only the battery connector, SSD cable, and SSD carrier need removed.
I agree with the last comment. But I would prefer loosening the center battery and lifting it up to guide the trackpad cable easily. This also makes it easier to reinsert it into the connector during reassembly.
Steps 24-34 are UNNECESSARY for this repair! Removing the adhesive portion of the battery is not required to remove the trackpad. Just lift up the top part of the battery that is screwed in and unplug the trackpad cable.