I wish I had instructions or saw a video when I put my first together!! I think I made most of the possible mistakes all in the first attempt. Including putting the plastic runners in the bottom bee space instead of in the top and then wondering why the frames protruded!
I recommend using a crown board to check the squareness of the box as it is exactly the size of the box as well as being the only part that doesn't need assembly so you can't get it wrong.
Don't slither off to the shed to build the first one, do it in front of the other half, avoiding the "what? you have only built one box, but you have been out there for an hour?"