After scratching the 6-ft diameter in the dirt, I began laying the blocks so the inside would remain 6-ft. It took 17 blocks. I kept the keyhole as small as I could, but still allow me room to step up to where the central basket will be. The second course took 17 blocks as well. These were set over the gap in the previous.
The 3rd, and last course - passed its first CatScan!
Added the central basket - A 1-ft diameter frame for compost and water when the garden is growing! The inside garden soil is made by soaking cardboard and other compostables in a 3:1 Brown:Green (Carbon:Nitrogen) ratio.
It takes a LOT of material to fill it up!
I topped it with all the ready compost from the compost bin.
Since it only took 51 blocks total for the 3 courses, i've got almost half the blocks needed for the second keyhole!