Leave the second card in the corner between the two left cells.
If using an iOpener, reheat it and apply it to the central battery cells.
As before, leave the iOpener in each position for about a minute, reheating in between, to heat each half of the center cells.
In the following steps, you can either use a third card, or the card from the right corner. The right corner adhesive should be dry/cool enough that the cells can easily be pulled up again when needed.