First, attach the included ribbon cable to the HQ Camera, or use one you have handy. Then attach the HQ Camera to the HQ Camera Mount Pro. You can put the lens on now, or wait a while, whichever you prefer. It doesn't get in the way. The official HQ Camera Mount Pro assembly instructions are available here (they're helpful for finding the right bolts to use).

Attach the camera ribbon cable to the Pi 4. Remember, the silver connectors face towards the HDMI ports on the Pi.

Attach the ICE Tower to the Raspberry Pi 4 following the enclosed instruction booklet. Leave off the lower base plate, though, since that's where we'll attach the camera mount.

Now take a break and use the Raspberry Pi Imager on a separate computer to burn the Raspberry Pi OS onto the flash drive. I recommend using the 32-bit release. The Pi 4 now supports booting from USB, so this will work with new Pi 4s. If you have an older Pi 4 without the updated firmware, you'll need to follow a procedure to update the firmware yourself (not documented here). Spoiler: it's a lot easier to use a new Pi 4.

Once the flash drive is ready, put it in one of the two USB-C ports on the Pi 4. Those are the ones with the blue spacers.

Now that the bits are in place, we can go back to assembling.

Connect three 20mm brass standoffs together so they are long enough for the Hack3r plate to clear the fan. Make two of these.

Screw those standoffs onto the two ICE Tower mounting bolts opposite the GPIO headers.

Things are coming together now! Press the tall Pi headers into one end of the Black Hat Hack3r ribbon cable. This provides the clearance to connect the Hack3r to the Pi.

Attach the other end of the cable to the Hack3r plate.

Attach the Hack3r plate to the standoffs in the orientation shown.

Next, attach the Hyperpixel display to the Hack3r panel. It will protrude to the left in the above picture. Be very careful not to press down on the glass. Grasp the PCB at the sides and slowly wiggle it onto the pins. You can see the final position here.