I keep my money in property.
Difficult to grasp because your one criteria immediately flies out of the window, namely that the savings vehicle must be liquid. But the property I have is extremely liquid, properties sell in under a month here. They key is always location and I am earning a monthly rental on the property anyway.
Also if you want to save a million for example in a normal vanilla savings vehicle, you have to use your own money. if you want to save using a property, a bank is willing to give you the money right at the beginning. The return on property may be significantly lower than other vehicles, but there are tax savings, capital growth of the property and the fact you don't have to use your own money up front to purchase the asset.
Anyway just putting it out there, its what I do, but others may be a bit adverse to doing it this way.