When visiting Paris about a month ago, I was able to see the wood
fired oven in the basement of the original Poilane bakery at 8 rue du
Cherche-Midi in Paris. I asked the baker how he made steam in his
oven. He ladled some water out of a bucket, dumped it into a cast
iron depression in the floor of the oven over the coals, and fitted
the wooden door into the oven opening. No spray bottles, no ice
cubes, just a pot of boiling water in the oven.
If it's good enough for Poilane, it's good enough for me!
Dan