It depends. If you are using mortar then thinner would be better but if you are using sand and then planting in the cracks thinker 1 1/2-2" would be better. Anyone can do anything it depends how much stamina you possess or how impatient you get. Your soil base determines if you use a base of gravel or sand. Gravel is more stable, sand is less. You probably will not be having frost heaves so it depends on how hard you want to work. Lots of labor involved and mortaring can become messy and removing it from the stone. I would go with a 3" gravel base then 2" of sand. 30 X 12 is a huge undertaking. Wear gloves. Here is a link that might be useful: Propagating Perennials

Good morning Colby, Your base thickness sounds appropriate for your climate ( this is what we use and we are also located in N. CA.) I'd go closer to the 3" rather than the 2" for the 3/4" crushed gravel. If you have access to 3/4" class II base rock that would be preferable to straight gravel. Class II base has some fines mixed into the gravel that aids in binding the base together when it is compacted. Additional recommendations , : compact the soil below your sub base. Especially if it is highly organic. Loamy soil to clay like soil is made up of decomposing matter that continues to decompose as it ages. This is one example of why dry lay patios eventually become uneven and sink , it is one of the reasons why the topsoil layer is commonly removed when laying a patio. I support the filter fabric method between the compacted gravel base and the sand layer, especially if you use straight gravel which even when it is compacted still has minimal air gaps for the sand to filtrate downwards. 1x6 plastic border will warp out of shape very quickly once a downward and sideward load is pushed against it. You will need to either augment the 1x6 with additional shear or additional equal loading pressure or use a more appropriate size thickness to support the pressure. Some methods may include digging a perimeter concrete footing - sort of like a curb that is located below and under the edge of the flagstone. Or beefing up the edging to a 2x material or countering the side pressing load by edging the edging with rock or cobbles or some other stable + grounded methods.

That is a well-known poolside finish - good traction. Have you tried scrubbing it really well? Sandstone has to be sealed, it stains easily (porous), and if it gets wet and freezes, it can shed layers. If you have a good concrete base, you can set extremely thin slabs of sandstone in thin mortar. You will raise the patio an inch or so, which will cause drainage problems for the pool. Pool borders have to be higher than the surroundings or rainwater and crud flows into the pool and you have unending filter and algae problems. Setting slabs that are thick enough for foot traffic on sand would require a couple inches of sand and 1.5 inch slabs and look really weird, as well as causing dirt problems for the pool. You don't want dirt next to the pool. Trust me. Walking across planting to get to the pool will track crud into the pool and increase the cleaning effort. Ripping out that existing border gets you into all kinds of problems, because you can't do it without high risk of damaging the tile ... and removing damaged tile risks damaging the pool's surface and it cascades from there. Basically, scrub it really well and live with it until you have enough money for a complete patio removal and replacement or look into the acrylic re-surfacing for pool decks (fake flagstone) that only raise the surface a tiny bit.

Kristie, We just enlarged our patio and had flagstone installed for the patio & a 5' walkway around the side of the house. Here are a few photos. The first shows the flagstone without the grout. The June 3 photo was made looking down from the back porch; the stones look a bit gray as it was prior to it being washed after the grout was put in. Another is the finished project (we still have some things to finish in the landscaping, photographed yesterday (June 26), but it doesn't really show all of the patio. We have a pretty good slope on our lot with a lot of open space between the patio & woods, and we had to keep some slope for drainage. It still is very "level" in terms of the stone. Our table & chairs, flower pots, etc sit very level on it. You have to expect a few rough spots because it's natural stone. The only thing I can suggest is just make sure your installer understands what you want in terms of the finished job & you reject any stones with a rougher texture than you'd like.