To dhengar: I like your idea. Very interesting. The soil should stand vertical in the drilled holes, because it is a cohesive material. A snag would be that the soil under the base would heave on freezing and lift the 16" x 30" cap together with the drilled piers. I had been thinking of something similar to what you suggest, but with a couple of helical piles under the base, but that too would be subject to frost heave under the concrete base, lifting the base and piles.
To mijowe: When Isaiah says "stone of sure foundation", does he give any details of how to accomplish that? I am sure he was not thinking in terms of frost heave, so that may not be too useful even if he did give details, much as I admire Isaiah.
To OldBldgGuy: If nature was perfectly uniform and symmetrical, then you would be right, that it may not matter that much if the top of the base is higher in summer then winter. But since soil is not uniform, the frost heave is not uniform i.e. each corner of the base may lift a different amount than another corner, so it will end up not level. Also, it never settles down exactly into the position it started in. After just a few seasons, the lack of levelness due to frost action in the cohesive soil may not be particularly noticeable, but after a number of years it will be. By 25 years, it will likely be quite noticeable. I am sure you would agree with me that if you want a base that is designed to stay level for at least 25 years or more, and the soil is clay, then the foundation should extend down to 1.2 m (Toronto area frost depth) in accordance with good engineering and construction practice in the Toronto area. If you are prepared to rebuild the base every 10 to 25 years, then the 1.2 m depth may perhaps not be essential.