The actual square size is 1 7/8", not 2" as advertised. I measured with a ruler. To verify, I also measured the total width across all squares to be about 14 7/8". A chess board with exactly 2" squares would have measured 16" total width across.
The board is made of cardboard but not the same type of cardboard as a Amazon or USPS Priority mail shipping box. This board is like stiff glossy cardboard. It's hard to draw a comparison with something familiar. It's kinda like a thick photographic poster stock type of cardboard. The board has a good degree of stiffness, not flimsy like say a cereal box.
As others have noted, it likely won't lie completely flat. You could probably flex it to some degree to make it lie flatter. With use, I would expect the board to get broken in and lie flatter over time.
For $4, my expectations weren't high. I wanted a portable (either folding or rollup) board with slightly smaller squares than a 2 1/4" vinyl board that's common in the US. I got that, though a little smaller than expected.
There is a certain aesthetic and feel when a chessboard is matched to a chess set. If the squares are too small, the pieces seem cramped. If the squares are too large, the board feels overly spacious. A board should be paired to a set and square size is an important consideration. That's why I raise the issue, as this will be important to some people.