Following a question from Bill in comments.........
Before I start, ignore the drilled hole in the first few pictures. I have used a similar method for 1:144 aircraft, but I wanted to check that the base was heavy enough for 1:100 diecasts. I'm still grinning..........
Materials: Jam jar lid (60mm diameter), plastic(ish) pole, a crocodile clip and some lead (ignore the hole).
Melt the lead and pour it into the lid on a level surface (a thank you to Giles, who laid my stone floor) up to just below the rim (ignore the hole).
Whilst you have the gas on, holding the crocodile clip with a pair of pliers, heat up the base end of the crocodile clip until it changes colour. It does not have to be red, just changing colour, you want to melt it into the plastic not burn the plastic. Then push the clip gently but firmly into the plastic pole. This 'plastic' pole is actually a venetian blind opening thingy that I laid aside when the blind was replaced - it's always a good idea to keep such things.
Now drill the hole for the 'plastic' pole (the hole!).
Normally, I would have spray painted the base, for a finish, and stuck it all together before showing the final assembly, but as this is a bit of home grown precision engineering, I'll show you the construction before I disassemble it for painting (remember that hole?).