First of all, let me say that plywood has many beekeeping advocates - I'm just not one of them.
What if I made nuc boxes from it.
It can certainly be used to make nuc boxes - here are a couple of shots of one divided nuc design in which I used 10mm plywood. It has a fixed base which has helped to keep the walls straight. I made 8 of them, and they're still in use.
Do you think screwing it together would keep it in shape?
Yes - that's the method I used in this experimental Long Hive (long since modified - but again, still in use) in which I glued 2 bowed pieces together so that one bow cancelled out the other, making 20mm plywood in the process - you can see how many woodscrews I used !
So to make tops or bottoms, the process is to glue the pallet pieces together?
Well - it depends ...
This is how I make large, wide planks (these were for a Long Hive) using pallet wood - 'cause we don't have the luxury of your Oregon forests over here ...
Simply run the planks across a router table to clean-up the edges, glue the edges together on a flat surface with weights on top to hold the planks flat - then pull them together tightly with clamps.
But - for a floor, that's overkill. Here is how I make bases - the planks are simply nailed to 2 thick battens running at 90 degrees to the planks, which also then act as 'feet'. Gaps don't matter, as it's only the floor.
That's fine if you want a solid floor. If you should want to use an Open Mesh Floor, then I make a 3-sided skirt to fit between the OMF and the solid base. A sheet of Correx, suitably cut, can then be slid on top of the solid floor to catch the debris, and thus easily removed and cleaned-off without disturbing the hive. A fourth (detachable) side to the skirt can be placed in position for when first introducing a new colony (to stop them from 'getting lost' underneath the mesh), and for whenever severe winds are forecast.
I didn't follow with the plastic.
Ok - this was an early test run of using a plastic 'soft top'. I was a little concerned about feeding through the plastic, so made a closeable flap from the lid of a butter carton, and made a simple hinge from tape.
It worked well enough, so I then went ahead and made a more permanent version.
However, I didn't much fancy placing inverted jar feeders directly onto the top bars, in case they should then leak and empty into the hive. So I made-up some beespace 'shims' from plywood offcuts and placed these under the jars. So far, so good - except that when I came to refill the jars, some bees had glued propolis between the shim and feeder lid, so that the shims then had a tendency to slide across the plastic. To prevent this, I then attached some thick plastic offcuts underneath the shims with drawing pins (thumb tacks) and then secured this onto the soft top with tape. Bit of a bodge, but then, this is still 'work in progress'. :)
Perhaps I should also mention that my reason for having 4 feeder jars on each hive (2 per nuc), is that we don't have your large Mason jars over here - so I use the largest jars we have - 1 pint - so that 1/2 gallon of syrup can be given in one go. That's the best I can achieve with what's easily available.
Hope at least some of the above clarifies my earlier post.
Best regards, LJ