A couple of things that we learned while trying to solder the wiring, is that it is vitally important for everything to be as compact as possible, bundle wires together using rubber bands or shrink wrap, minimize wire length as much as possible, packing together boards and chips, are all things that should be done in order to achieve this.

It's also very important that you keep track of which wires are positive and negative. If the charging board isn't correctly wired to the Pico, it can overheat and melt wires, and if positive and ground is switched you can damage your components.

Super glue and hot glue are very important as well, super glue can be used to secure wires and chips to wherever they need to be, and hot glue can be used to insulate wires, pins, and any other exposed electric component.