Are the particle issues coming from the cutting boards just from the slate (black) cutting boards or also an issue with the natural cutting boards?

My black board started to release flakes when cutting after years of ownership. I have never noticed flakes from my natural ones. Although I can’t rule out that I just never saw the flakes due to the lighter color, I believe The truth is that the natural ones don’t flake like the black. I think I would have noticed natural-color flakes, too. I had had these cutting boards 10 years now and love the natural ones.

Are these nontoxic cutting boards, no bpa, etc? Thanks!

I would not consider these as nontoxic since a large component of the board is a chemical resin. To date i have not seen any evidence that epicurean studied ingesting the stuff well. All I have seen is misleading marketing.

Does this board have the rubber corners to keep the board from slipping on the counter?

No, this board does not have the rubber corners. Those only come with their non-slip series of Epicurean boards. I, as well, have one of these boards and have never felt that slippage was an issue, even while cutting. This board is part of the Kitchen Series, which is a smooth surface board on both sides.