The flat battery indicator cable sits directly underneath the headphone jack/port and then goes to the top on the right side of the battery screw. If you forgot to put it underneath the port when reinserting the logic board (which leads to the battery not fitting), carefully slide it underneath the port into the small available space with a spudger.

This one took me a moment to figure out. I also have the foam pad and couldn't see where the socket begins. Use the flat end of the spudger and go underneath the red/black cable part close to the socket, then slowly lift it up until it loosens a little, then do the same on the other side.