Wood cutting boards can easily warp if you let too much moisture get to them for extended periods of time. Fortunately, you can fix it by warping it back with a couple household items.
Photo by Jameson Fink.
Despite what you may have heard, a warped cutting board is not irreparable as long as the warp isn't too severe. If your roommate left your cutting board in a water-filled sink for several days, it might be too late, but otherwise Leslie Stephens at Food52 suggests you can fix it with your iron:
To fix a warped wooden board, place a damp cloth over the warped area and iron it as you would any fabric. Repeat until the board is un-warped. Once the warp is gone, allow it to dry completely before using.
Once you're ready to let it dry, Grant Chen at CuttingBoard.com recommends you put some weight on top of it to ensure it dries flat. You have to be cautious as you iron your cutting board, however, because it's possible that it can crack if you try to warp it back too fast. If it does, there's still something you can do about that. Cutting boards can last for generations if they're taken care of properly, so don't toss it out until you know it can't be saved.