Wood will expand and contract across the grain, and a wide panel made of solid wood could change width by a half of an inch, warping the door frame. By allowing the wood panel to float, it can expand and contract without damaging the door.
Put trimmed and cleaned green beans in the steamer basket, set over the boiling water, cover, and steam until tender to the bite, 3 to 5 minutes (depending, again, on how crisp or tender you like your green beans).
SautÃ© the beans: Heat the oil in a large skillet over medium-high heat until shimmering. Add green beans and cook, stirring often, until the beans are bright and glossy, 5 to 7 minutes. Season the beans: Add the garlic and salt. Cook, stirring constantly, until the garlic is fragrant, about 30 seconds. Steam the beans: Add the water and immediately cover. Cook covered until the beans are bright green and crisp-tender, 1 to 2 minutes. Serve: Add the red pepper flakes, if using, and serve immediately.