There has been a lot said about the joints in the flow hive boxes. I myself was not that impressed that I had to rasp the box joints to get them fitting.
Having just finished making some brood boxs I have to advise things are not always plain sailing.
I had a lot of trouble with light, moisture absorbent wood like pine. I was using scrap to perfect my box joints and found that joints cut one day and fitted nicely could not accept a joint cut the following day. Using the same wood and technique.
With 13 tails and recesses in a joint I found that the difference between a snug fit and a non fit was as little as 1/1000th of an inch for each cut.
Tails or recesses cut on a more humid day or with a saw blade temperature difference accounted for as much as 5/1000 th of an inch. That is a fit or non fit. Luckily I could measure and cut to these tolerances
While the Sheoak which I used is very stable, I made sure the joints for each box was completed without a stop. The first boxes joints I made are not a good fit (they go together with persuasion) with the box made two days later.
Boxs made with other joints are much more tolerant of differing sizes.
Just saying. Maybe the joints were good one day at the factory but mixed with joints cut on a different day not good.