The Honeycomb pins have a lot of holding power. You can place the ‘crown’ of the material down and then pin the edges down.
Of course that doesn’t prevent the warp from rebounding when you remove it. Acclimating the material like @rpegg suggests is best. I have ‘accelerated’ the process by supporting the edges and placing weight in the center to reverse the warp and leaving it overnight - or longer depending on the result.
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