Cut and build the foam boxDividers into a +, tabs into the base, walls dropped over the divider ends, legs pushed in. Fit the sensor and light-hole plugs.
Cut and glue the plywood baseMeasure the ply first. Glue the floor, walls and front strip, then the drawer. Screw the USB fan to the back.
Print the holders and racksFour of each on the P1S. Test one of each in a chamber before printing the rest.
Fit the lightsStick a strip loop round each rack, starting at the wire-drop corner. Feed each lead down through its light hole.
Fit the sensorsLay each chip against its wall over the notch. Run its ribbon down through the plug's slit.
Wire the drawerPi and breadboard on the tray. Sensors, lights and fan to the Pi and the USB charger behind the box, through the cable gaps.
Put it togetherLower the box into the base. Slide in the dish holders, set the racks 50 mm up and bolt them, then put the lid on.