The most important gluing step
The final thing I did at the end of day two was to glue the first vertical piece to the bottom shelf. It's essential that these two pieces form a true 90° angle, as the rest of the shelf will derive from this angle. I use very accurate stainless steel Shinwa squares from Japan for this step, as they have very precise tolerances. In this case, the wood was so straight that I only needed to use one square. I let the joint dry overnight under the heat lamps to ensure I would have an unbreakable joint to work with the next day.