First I leveled the slightly sloping ground with my box scraper. I left a very small slope so that rain would drain off and not pool.
Then I used my post hole digger to make some post holes. The ground is very rocky, so some holes are a bit shallower than I wanted, but they don't need much depth or structural strength for this application.
I cut some 8' pressure-treated 4x4 posts in half, put them in the holes, dumped concrete mix around them, and poured some water on top.
I cut all the posts to a level height and put pressure treated 2x6's on top to have a surface to which I could secure the canopy legs. Some deck screws with washers secure the feet to the ledge.
I set up the canopy and guyed out the corners.