Why does this happen?
When wood becomes wet the fibers swell and it becomes malleable. This can lead to warping, cupping or twisting. Water can also be the fix. Here are a couple of tips to help you fix your cutting board.
The Quickest Fix
First, rinse your board with warm water on both sides. Do not submerge it in water as this can damage your board.
Next, dry your board with a clean towel. Your board should be a little damp. This is okay. Lay your board on a flat surface so all the corners are touching the counter.
Next, you will need to put some heavy weight on your board. Not just the center. You will want to cover the entire board. You can place a towel, flat sheet pan or parchment paper on your board before placing the weight on top. This will keep your board nice and clean. You will need to leave your board with the weight on top for at least three days.
The Slow No-Risk Fix
Just turn your board over and lay it on a flat surface so the corners are pointed down. Now you just need to leave it alone for a few days. Your board will slowly flatten as the air will remove the moisture captured in your board.
Now that your board is flat don’t forget when you hand wash to wash both sides to prevent warping. Once you have towel dried your board, store it vertically to prevent water from pooling.