I wanted a "large" poster with "many" chess boards that I could cut out with scissors.
I gave you the tools to do this, leaving some work as an exercise for the supposedly self-employed.
You also neglected to specify the physical size of the poster; nor the physical size of the chessboards you wanted. I figured you'd do the math as I would, and produce an optimal tiling of chessboards for your needs.
Now, about those chessboards, they're kind of boring. You don't want to be competing with this:
$6 for a cheap board, but handcrafted wooden pieces!
Or this for $7:
You won't make it up on volume. I suggest you lean into what makes your system unique: You can 3D-print uniquely shaped pieces, and you can print uniquely styled chessboards. So see if you can make (or find, I guess) some unique chess piece styles; then try to find a board style to match. You might also consider buying plastic chess pieces like the latter link so you don't have to mass-print pawns.