Open It. Just the smell of that cedar will kick start the adrenalin rush.
The good part is that you can take your time, there no rush, no pressure, as being in UK you will be unlikely to get bees till spring.
You will have a great time putting together and when finished look at it and say “WOW that is so beautiful, and I did that”
The hardest part of any new venture is to start. Open the box and you are started . There are a lot of videos (two by Flowhive themselves) on Youtube on putting your box together. Down load the video you like the best or understand the best and follow the steps. ie watch a bit stop the vid, do the bit you have watched, start the vid watch another bit, stop the vid do that bit… until it is complete.
I would like to see a pic of your hive when it is done.