Next up we need to prepare two 12mm buttons for our shoulder L and R buttons.
Start by clipping two of the four legs from each button. Use a pair of flat pliers to flatten out the legs so they point out like in the photo. Secure the button to a pair of helping third hands and apply solder to each leg to tin them.
We'll need two sets of wires (four total) to measure about 14cm in length. Strip and tin the tips from each wire and thread them through one big piece of heat shrink tubing. This will keep the wires together in a neat bundle.
Solder wires to the legs of each button - Like before, use a pair of helping third hands to assist you. Polarity doesn't matter too much on these buttons, but you can reference the photo.