A flat 50mm round base since I now have models that are supposed to go on this size.
Besides the cross beams I've already used plenty of times in the past, this base is supported by adding many many small supports along the trim. While at first glance it might seem as a waste of material, it is actually not that many more supports that what auto-supporting it would give you since the centre is almost empty, and it does help prevent warping almost entirely. I'm not a physicist, so I don't really understand the science behind it, but it works really well, so I just do it.
There's also a slot for a 3x2mm magnet underneath.
