It’s a slab that I am attaching hairpin legs to. I used a small steam humidifier and put it under the cupped area (it was mostly cupped at one end). I left it there about an hour and it flattened out pretty nicely. It was approx 1" cupped (22"wide at that point). Now it is almost completely flat. I put some weight on it while it drys out. We’ll see what happens when i take the weight off… I tried to attach a pic but it wouldn’t upload.