How do I flatten a warped drawer bottom?

You could try soaking the wood with water .Then put on a flat surface with curved side up and apply weight to pus warp flat .add weight slowly so as not to crack the wood .

Wet it then place something heavy on top of the whole thing and let it dry it should go back if not do it again.

What the folks above haven't said is where to use the water! If you soak the entire board, it will take a lot longer to work. You want to soak the part of the wood where the fibers are most dense - which will cause them to widen and flatten out. It's pretty simple physics. So, making sure the entire piece is damp so it won't crack, soak the area in the center with a good bit of water - just puddle it down the middle. Let that sit for 20 or 30 minutes and then sop up what hasn't soaked in. Now, start pressing the wood. The compact fibers should have absorbed enough water to start expanding. Put the weight right in the center all the way down the length. As it flattens, you can move some of the weight off so that more of the wood is exposed and can dry. When you're sure it is dry and straight, you may want to seal it so this type of thing doesn't happen again. Best of luck!

try putting them outside on damp grass in sun - hot in summer would be best -lay them so curve is raised above grass- they may just flatten out by their own weight in the hot & damp -

I like what Jan suggested, it was what I was going to suggest. She gave excellent explanations as what to do. Good Luck! I always seem to have drawer bottoms that warp, but I usually catch them somehow before they get too bad and I just reverse them.

I tried using my clothes steamer & then put heavy weights on it. That seems to have done the trick. Thanks for all the advice!

Wrap the wood in moistened towels. Moisten one or two large towels and wrap them around the wood. For all of those just saying "wet to board" got to agree you have to have something to put the wet board in. You can't just pour water over it!