My previous sculptures have been laid on a cafeteria tray and glued to it; so the possibility of them falling over hasn’t arisen.
Now, however, I’m dealing with the human body, which stands upright on two legs.
For sculptors who deal in the human frame and similar upright sculptures, the answer will be well rehearsed. If there is minimal contact between the sculpture and the plinth, you need to incorporate some kind of support into the sculpture (see Venus below), or else use hidden fixings.
Classical statues sometimes leaned against a tree stump or had folds of clothing that draped the ground.
Today, metal sculptures can be welded to a plinth, and have hidden pins set in concrete. Sculptors working in stone use glued pins with a template for drilling two holes in the right place in the wall or plinth. That’s what memorial masons do to keep gravestones upright.
However, I’ve never established how ‘floating shelves stay up. Something to do with pins I think.
In the case of my resin statues, I will fill them with expanding foam that will solidify. Each leg is then drilled, and a threaded metal pins is inserted into it. The pins then go into the plinth and are held in place with a bolt and outsize washers.
Now all I have to consider is how to secure the base of the plinth so it doesn’t fall over. I’ve never seen anyone push a plinth in a gallery. People walk gingerly around them, just as they never get too close to a parked motorcycle in the street.