I never saw this thread either.

I have done several ornamental raised beds with concrete blocks. I dug a trench the depth of the bottom block. Back fill that trench with pea gravel and or sand such that the block will be buried half way when placed. If you're a bit OCD like me put a bubble stick over the block and make the rows dead flat and level to the world. Tap each block down with a mallet and move to the next.

There is a nice product by Quikrete to make dry-stacked (without mortar) block solid and remove the block lines called Quickwall.

I would not pour a foundation or compact a layer of sand and lime under the garden for drainage reasons. A better route would be to mix sand and organic matter into the native soil then build your garden soil compost mix over that.

Two of my main theories are NEVER to walk on or in a raised bed and not to stop roots from going down deep by putting weed fabric or sheeting at the bottom of the beds.