I would till up the area and take out all the weeds and grass. Then I would lay a plastic tarp to keep the grass from growing through. Then pour the gravel.
You need some type of boarder to contain the gravel. If your patio is going to be level with the surrounding area (not a step up), then you will need to excavate several inches of soil. The amount of soil really depends on where you live, how much rain you get, and what your soil is like. Once you have excavated and leveled the area, put down a layer of landscape fabric to help prevent weeds. Start with a layer of base material. It is a mixture of crushed stone and stone dust. Around here it's called "dense grade base." Don't use the stuff the big box stores call paver base. Get it delivered from the same place you will get the gravel from. Tamp it in 2" layers. This base layer will help with drainage and provide a sold base for the gravel. Next, install whatever type of boarder you want. Finally, finish with 2-3" of the gravel you want. If you make the gravel too deep, it will be difficult to level furniture and walk on.
Map out the shape you want, dig up the grass. You will want at least an inch or two of sand for the gravel to settle into and help level the area. Put down landscaper plastic to keep the rocks from sinking into the soil and keep weeds out. Put down the gravel to the depths you want. Make sure to have some kind of border to keep the gravel in place in the area. Gravel can make placing furniture hard, so you may want to put some pavers down where at least the chairs are going to sit so that they don't rock or become unbalanced when you sit down. I hope this helps you some Carl!
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