Nice idea
Ideas on creating very large boards (physically)

I had the board printed on some piece of floor vinyl with some own pattern - that was not too disturbing - but it is a bit too shiny with lamps or sunlight around, so I will improve on that some time.

Buy 4 boards, cut the edges off and glue them together?
Nice idea but will it stay in one piece when lifted? Even when plugged like this one?

I'd like to mention this new option for people looking into large boards for chess variants:
https://www.houseofstaunton.com/nextgen-pawn-10x10-vinyl-tournament-chessboard-2-25.html

I'd like to mention this new option for people looking into large boards for chess variants:
https://www.houseofstaunton.com/nextgen-pawn-10x10-vinyl-tournament-chessboard-2-25.html
I can only recommend this and played Grand Chess with it on Friday with a friend OTB.
Note that nowadays ordering prints on vinyl is not expensive at all. Last year I did order a large (122cm x 244cm) vinyl 'banner' that had my family tree printed on it, decorated with color images of the towns where my various ancestors lived.The printing quality was superb. For a 52cm x 100cm banner they currenly charge only 15 euro. This should easily fit a 10x8 board, or even a 10x10 plus a 10x8 board, if you use 5cm squares. (For my taste the squares in the photograph above are a bit too large for the pieces shown on them.) All you have to do is draw the board(s) you want in MS Paint, upload it in a standard image format to their website, pay them and wait for it to be delivered at your doorstep.

Thanks for the link @HGMuller. I can only see predefined sizes, but perhaps by contacting them, one could find out if customized sizes are also possible.
Yes, it is a Dutch company. But I am sure similar services must exist in other countries as well. 76 x 122 cm is huge. Should be good for two pretty large 10x8 boards (7cm squares?) The stuff can be very easily cut to size with a Stanley knife and a ruler.
Yes, the website mentioned in #9 is in Dutch, but if you click on the tiny flag near top right you can change to many different countries/languages. Here for example is the same page in English in the UK version: https://www.vistaprint.co.uk/signs-posters/vinyl-banners
By very large, I mean of course squares of normal size but many of them.
I have a very nice wooden board with 10 by 10 squares, where a single square is almost 6cm by 6cm which is very comfortable. But this will always be custom made and quite expensive.
And a challenge to transport without causing damage.
So I made two pictures:
http://scrybqj.com/images_diversen/12x12board_with_edge.jpg
http://scrybqj.com/images_diversen/16x16board_with_edge.jpg
(I picked the colours from a picture of my real chess board and filled in the entire pattern using Paint)
My local repro could easily print this on carton.
I asked for the possibility to print on vinyl and that was possible, since carton will get wrinkled after some time.
And I even found a company (Kwantum and they also sell the vinyl) that is willing to print on wood for whatever size one has in mind.
One other thing I found on internet:
http://www.carwrapdirect.com/chequered-flag-style-vinyl-wrap-with-adt/