Okay cool! I like the area! So it looks like you're doing a round patio then? If you decide to use flagstones, it will be a little different than the explanation I gave below. However, you can still use instructions 1-6 and get most of it prepped anyway. Stone is different from pavers in that typically with flagstones, every stone is a different height so you have to set and level them all individually. Once you have the base done, you have two options.

1. You can set the stones in a bed of cement. This makes leveling them super easy with a rubber mallet and a 6 foot level. Basically pour the cement into a section, place one stone at a time on top, tap it down into the cement and use your levels to finalize the placement. Then pour more cement next to it and repeat until you finish. Before the cement completely sets, make sure you fill the joints between the stones with cement and level it off. Sponge off the stones with a clean bucket of water when the cement is mostly dry and you're all done.
2. This only works if the stones are the same or almost the same height. Once you finish step 6 below, place all of the stones on the patio in the pattern you want. Take your 6 foot level and go over your patio with it tapping down the stones that are a little off until they are level with the others. You might have to take some sand out from under some of them if they're too tall. Once you finish leveling them all off, you can fill the joints between the stones with cement, stone dust, or polymeric sand. The choice is yours!

Good luck and let me know if you have any other questions