Measue each wire so that you have enough slack to reach the PowerBoost while the lid is open. Take note of the position of the lid, PowerBoost and slide switch.
To make room for the slide switch, we'll need to bend the leads upward so they can fit inside the enclosure. Use flat pliers to bend all three leads upwards and cut off the excess.
Cover the soldered leads with heat shrink tubes and apply heat with something like a Hot Air Station.
Thread the slide switch wires through the middle port opening. You may need to widen the port depending on your printer tolerence. It should snap into place with a bit of force.
Tin and solder the +5V from the monitor to the + on the PowerBoost. Connect GND on the monitor to the - pin on the PowerBoost.
Solder EN and GND on the PowerBoost to each lead on the slide switch.
Use a piece of gaffers tape to secure the battery to the Lid. Use another set of #4-40 screw to attach the Lid to the enclosure.
To attach the monitor to a tripod, we can use a thread adapter with female 1/4" thread to male 3/8" thread. There are two slots on the enclosure to add the thread adapters to allow portrait and landscape setups.
To power the monitor through regular camera batteries like a canon, nikon or panisonic; check out the guide for adding a UBEC DC/DC Step-Down Converter: