For a battery repair with the heat method, you can start to unglue the center battery cells from the sides, you can see the darker metal plate protecting the trackpad and will not mistake it for the glue. This is safer if you are afraid to damage the trackpad by hitting them with the cards, especially if you operate from "below", ie bottom side of computer during the repair

For a battery repair with the heat method, I needed to remove the speakers, but not the connectors, just unscrew the speaker and put them away when working on the battery

For a battery repair with the heat method, as indicated in other comments on prior steps, you may skip this step, just unscrew the speaker and put it away when working on the battery. For this specific left speaker - on the right during the repair - you need to be careful with the protruding bit from the frame when moving the cable. Just guide the cable above or below as needed during the repair, to prevent to damage the cable with this protruding part.

For a battery repair with the heat method, as indicated in other comments on prior steps, you may skip this step, just unscrew the speaker and put it away when working on the battery

This step was not necessary for a battery repair using the heat method. You can keep the connectors attached, just unscrew the speakers and put them aside by bending slightly the connectors. Just be careful when working to remove the glue with a card, you may need to apply a bit of force, so make sure not to damage the speakers wires

This step was not necessary for my successful battery repair using the heat method. My guess to include this step is that you may damage the IO connector at a later stage if you need to use a card in this area to remove the center battery cells. These were very well glued in my case, so it is true you need to work a lot with 2 cards, but I was able to unglue them from the sides

This step was not necessary for a successful battery repair using the heat method in my case

I also did not remove this connector for a successful battery repair using the heat method

Reading the comments before starting a battery repair, I decided to use the heat method instead of the solvent and skipped steps 8-9-10-11-12. It was still necessary to remove the speakers, but you can let them connected, provided they are "bent" out of the way when you work to remove the battery. For the IO connector you may want to remove it if you need to use a card in this area to remove the battery and you are afraid to damage it. It was not necessary in may case. The solvent was still useful to remove traces of glue.

If your are not familiar with those repairs, and as with most of those connections, I recommend to take the time to observe your computer and the pictures from the tutorial, reading instructions and comments before starting each step. This battery connector needs both a bit of force and of precision. For a battery repair the connection of the new battery is a bit more tricky, you need to have your battery in the right position and to force it a bit the connector