You may have made a list of the top mistakes there bosch. There is a ton of information on the interweb and books: do not spend any money before you have a more educated idea of how to proceed.

You just want a flagstone path, or an area of flagstone?

I do think that in CA you can avoid option C, but I'm thinking that what you have is a drainage problem, not a support problem, and you might want to address that first.

KarinL

@KarenL - I'm just looking for something like this, in the center of the picture are those stone "stepping islands" -

http://www.goingnativegardentour.org/GNGT/Garden.php?year=2011&gid=serene

I found the stones I want, about 1.5'x1.5' Bouquet Canyon Tumbled - after talking with the person at the rockery I'm going to dig a column underneath each stone about the width of the stone, and about a 8 inches deep, fill it with 6-7 inches of the rock from the pile I have as foundation, then put about a 1-2 inch layer of sand on top to level the stone out.

The soil not on the lawn area is hard-packed adobe that stays solid even after heavy rains - there's already some stones/bricks in the backyard placed on bare ground that don't budge.

I won't have any flooding issues with the house, if anything I might drown some plants come the next heavy rain.

@inkognito - I've searched all over the web and can't find anything for this kind of a "stone island" path...everything is about solid flagstone paths that are all flagstone from edge to edge. I just want some stepping stones to make a walking path with 4-6 inches between that will be filled with mulch (or over time, maybe some kind of creeping groundcover plant).

Thanks to both for responding.

Here is a link that might be useful: Sample Stones

I kind of doubt you need to do that much digging, especially as your sand will immediately - I think - disappear as it just falls into the gaps among your rocks.

But sounds like you're working it out.

KarinL

I'm not a pro designer, but thought I'd respond since your inspiration pic looks a lot like the garden we had in our previous Calif. home (E. Bay adobe soil). I agree with karinl that you probably don't need to do much digging. We used only sand to set the stone on the adobe soil, then mulch was placed over the yard to hide the layer of sand.

It was still looking great 5 years later when we moved.

I don't know where you read/heard that the Three Rivers flagstone will leach iron, but it isn't an issue in the middle of a garden as a path, and it would be my first choice as the colors really pop, don't waste your time sealing it, just hose it off from time to time. I also wonder if you really need to pay the premium for a tumbled flagstone, the raw Three Rivers flagstone is cheaper and just as nice. In California USDA zone 9 locations, an inch or two of sand is all that is necessary for a leveling base of flagstone used as a stepping stone pathway.

If you have clay loam based soil that is too soft, you may have a drainage problem needing correcting, or are just overwatering the area. A clay loam soil is only too soft and subject to compaction after significant rains,(and this is really only an issue for planted areas, where you want to avoid soil compaction when the soil is wet, so you maintain good oxygen exchange and soil texture for plant roots). Even in the middle of winter after heavy rains, a clay soil is fully capable of supporting the weight of flagstone pavers without problems of movement, but the sand base will help make them more stable. Weed fabric below a base material is really only appropriate/necessary when you are wanting a solid area of flagstone paving and want to reduce weed growth at the joints; when laying out more widely spaced flagstone as a path, I'd think you would want some low ground cover between the flagstones. If you don't, then use the weed fabric and mulch with gravel or decomposed granite between flagstone pavers.

If you are trying to lay flagstone stepping stones on a slope, there is considerably more attention to a stable base necessary, and I'd suggest you get professional help to install it for better results.

I'd also suggest you go to your local library or buy one of the Sunset or Ortho gardening books that address landscaping and dry laid flagstone paving, they both cover all the issues you will likely face in your installation, and are generally a more reliable source of information than asking questions on the internet.

If you are really interested in the best methods for installing a lower water use garden using California natives, you should also do some reading up on issues of soil drainage, best time of year for planting, how and when to water, importance of mulching, etc., as there are better ways to do this to save time, money and water.