place the joystick, Start, Select, A and B button on the top and solder them.

Solder the short piece of wire on the speaker and the 2 holes of the GameOn next to the speaker symbol. This can be done in the back to hide the speaker. 

When mounting the shoulder buttons, some pressure is required in order to get them flush with the PCB. By design they should be mounted on the bottom. These buttons are optional since you can also configure the 2 pads on the bottom as touchpads. However in user test it was deemed more comfortable having those 2 buttons in place to hold on to the controller.