Admit I have been away from Beekeeping for some years, but when I assembled frames previously the wax foundation fully filled the frames.
Why the use of undersized foundation ?
The flow team promote the use of foundationless frames in the brood. A good %age of forum members prefer foundation, myself included. I’d suggest you stick with foundation as you remember. My preference is wax foundation over plastic foundation.
Most of us just use foundation. In the UK you have very nice pre-wired foundation (I had WBCs there 20 years ago), but it may be hard to get the good stuff in Langstroth sizing, which is what you need for a Flow hive. In that case you have a few choices:
Go foundationless - not recommended, even for us old-timers. It can be a lot of work. Yes, it is probably healthier for the bees, but their creativity can be so much work to correct.
Go with plastic foundation in Langstroth sizing. Again, I don’t like plastic all that much, and neither do the bees, although they will use it with no other choice.
Find some Langstroth foundation - best option. If it isn’t wired, you can wire it yourself using one of @JeffH’s videos for a homemade system.
Use British National foundation and only partially attach it to the frames. Things will be a bit hairy until the bees have secured it, but it should work if you trim the bottom part off (National is longer than Langstroth).
Beekeepers adapt, and older beekeepers adapt things better than most people expect. Welcome to the forum.
Don’t worry if there is a small gap at the bottom or sides of the foundation, bees will often use that as a quicker way to get to the other side of the frame. The main thing is to be sure to get the right size foundation for the frames.
For me, I use wooden frames and wire them then melt the wire into the wax foundation. The bees might leave the gap or build it in with their wax.
In prepping the plastic Flow Super frames I use a daggy but clean old paint brush and melt some wax and paint it onto the ends of the cells of the frames. Doing that will get the bees more interested in doing their thing in the super.
Well thought out and good questions, it will all come back to you as you go.
Cheers
You could use dalinno frames! It is new and coming from Denmark. You just put a wax sheet directly in the frame, it takes about two seconds. And there is no wiring.
You can still use the same. You just have to either find a supplier that makes Langstroth-sized foundation and frames, or cut down British National foundation and fit it Heath Robinson style. It will not reach the outer edges of Langstroth frames, but if you centre it and cut off the lower 1/2- to 1-inch (depending on your frames), you should be able to fit it in quite easily. The bees will eventually build out the outer edges with no big drama.
I would suggest using Google to get a phone number for Thorne bee supplies in the UK. If they don’t have Langstroth frames and foundation in stock, I am sure that they will know who does, as they are one of the biggest suppliers in the UK. Beekeepers love helping other beekeepers, and Thorne are no exception.
I would think that highly unlikely! However, their web site is pretty good and full of fascinating information. I am certain that they would help you, even if you buy a Flow hive (which they do not sell).