I prefer open framed wood, with no top plate, the speaker supported at each corner and the underside panel of the speaker allowed to resonate in free air.
Metal can work well, but the design and damping needs more attention in my view, so wood is an easier DIY option.
These are all I use, which have interchangeable spikes or swivelling feet, depending on the type of floor they are set on.
The tops have a large thin rubber disc, that contacts the speaker.