I had a fairly large plot that was about the size of two city lots. I would till around the border and scatter the seeds on the tilled soil. Always much better results that way.
It's technically not too late for this year, as there are still some later summer varieties that will still bloom. But, it's all about having the time.
Hope you'll post some pics if you decide to give it a try. I've really wanted to do more gardening this year, but am finding myself way short on time and motivation.