The OP might do well to consider moving the material around to make mounds, berms and trenches. Doing so he/she could create places to bring in soil for beds for particular types of gardening. Although I haven't worked much with decomposed granite myself, I think that it will support many types of plants as it is. But those plants that need a different soil can be nurtured with imported clay soils. In Alaska last year, I helped make some garden beds built up on a rock and gravel fill. The location was a beach that had been built up with a boulder retaining wall and backfilled. The 'soil' was very 'young', full of stuff like decomposed granite. After making the raised beds (we used a chainsaw mill to make the boards from yellow cedar), we filled them with whatever soil we could scratch up. We screened the soil to remove the stones and used the stones between the beds for walking paths. Hard work. Some vegetables did ok in that raw soil, and cold wet climate; lettuce and radish for example. We used kelp, sawdust, and humus from the forest as mulch and soil amendments. Very different than the clay back here in Boise. I wonder what climate the OP lives in.

I just wanted to update this thread.. I am now finally getting around to landscaping our back yard after many road blocks. So decomposed granite and crusher fines or “chat” are not the same thing. DG is a naturally occuring erosion process created by mother nature and time and the product result is smoothish rounded pieces compared to crushed fines which are rough, jagged edged pieces that show signs of manually being broken or crushed and that is exactly how crusher fines or chat are made, they are crushed and broken apart with heavy equipment. To reduce the risk of tracking in the fine particulates of DG into the house it is suggested to use a larger sized DG. For light duty pathways that may never see the use of a wheelbarrow or trailer running over it then a 1/4” DG or crusher fines can be used but for utility pathways then a 3/8” DG or crusher fine will want to be used. There is this great little E book called “Decomposed Granite…..” by leslie patten and it goes over how to install a long lasting DG patio with proper road base installation and DG installation and there are no stabilizers needed or weed barrier and most surprising and contrary to popular belief is that you do not in fact install 2”-4” of decomposed granite. I highly recommend getting her Ebook and learning more about how to install DG using this method. I now suspect the reason DG is not widely sold in Utah has to do with the water retention + heavy moisture = slow draining so you end up with standing water and mud pits. The chat or crusher fines however are usually filled with sand or dirt to give it a denser compaction ability and to offer color variation. so for the most part after going back and looking at my original sources local to Utah for ”decomposed granite” I have since discovered some of the places are actually selling crushed fines and not decomposed granite. I can now identify the distinct characteristics between the two products. it is my understanding that installing anything less than 3/8” DG or crusher fines can result in a very soft and mushy ground cover and should be reserved for use in garden beds or used in areas that have imbedded paver stones and see minimal traffic. i hope this helps others who may stumble upon this!

Base thicknesses vary, depending on where you live (freeze/thaw cycle), but here in Chicago we would normally have 10" of total excavation for a brick patio with 6 1/2" of CA-6 gravel base, 1" of bedding sand and then the brick. Your attached photo shows the correct limestone for a patio base. But regardless of where you are if you don't do all the excavation now you will have to remove massive amounts of material to get to the proper depth later. Decomposed granite makes a very nice patio and is all the rage right now in the Midwest. If you opt for that scenario, then simply excavate 4-5", lay down a soil separator, spread and compact your limestone and then add the decomposed granite. 3" of limestone and 2" of granite works nicely. Compact the granite and you are "good to go" Here is a decomposed granite pathway, done in 2006 that I photographed a couple of years ago. The only downside is that they are not kind to bare feet. Otherwise they are a great aesthetic.

If you are handy with a saw and screw gun, you can build a form out of some melamine shelving or something, strong enough to maintain its shape, but not break apart from the weight of pour. Caulk the inside corners. Its how concrete counters are made. Pour the concrete in, mixed to a flowable slump, and let it sit for a day or two. Unscrew form sides and flip it over. If you want it to be even cooler, line your forms with textured panels or something and it will resemble the pattern. Even a huge maple leaf if your into that type of thing. Its easy don't be scared!