Use a standard strap to pre-bend the wood, then wrap it around any form
Michael Fortune’s steam-bending technique does away with the traditional compression-strap method. He uses a compression strap, but only to pre-bend the wood. After that, his method takes a nontraditional twist. He pre-bends the wood in opposite directions, breaking the lignin bonds and making it possible to bend, twist, and form it to unusual shapes.
From Fine Woodworking #193