Ok,
I am in the planning/designing/soil prep stage of making a fairly large flowerbed and I'm hoping to make at least a portion of it a succulent/cacti area - I have several succulent containers that will be placed in the bed to add interest, but I'd really like to plant hardy hen and chicks, small cacti (can't remember the name but I know they're hardy!), sedum (the tall ones that flower in fall) and sedum (several different ground covers) in the ground. I dug a hole to fill with water and check the drainage in the area I want to plant the succulents and there was about a 2" layer of "brown" topsoil, 6-8" of red/brown clayish dirt with random clods of "thicker" clay (it's the same color as the surrounding soil but is much more dense and slimy, not quite modeling clay, but close) and at about 10-12" I hit grey CLAY clay that I am certain I could actually sculpt with. I had to chip at it and scrape with a curved chisel type thing to get to the right depth - and then it took more than 24hours for the hole to drain after I filled it with water the first time - I didn't bother filling it again.

I have several ideas on how I could still make a succulent "garden" work but I'm not sure of the viability of those ideas...or if there's maybe something I haven't thought of.

1) could I remove the "modeling clay" clumps or even all of the native soil to a depth of 12-18" in the area I want to plant succulents and fill in with a well draining mix? Or would excess water pool where the well draining mix meets the grey super clay and cause root rot anyway? What soil "mix" would you suggest, I know peat is a "nono" but all of the commercially available mixes I have found in my area contain lots of peat.

2) or should I reconfigure my "design" and put my succulent area somewhere where there seems to be better drainage?
As I have been digging out grass and weeds and turning the soil over throughout the area it seems like there are pockets of sand or sand mixed with red dirt, and in some areas the grey clay seems to be deeper. Would these areas be better to plant the succulents? I will be digging in plenty of OM (commercially bought compost) throughout the flowerbed, is there a type/brand of OM that would improve the soil more quickly for the succulent area? Or a kind that I should avoid?

3) could I make the succulent area raised? If so, how raised?

As a side question, when I dug out some ill placed bushes I noticed that whoever planted them seems to have mixed in copious amounts of sand in the planting hole, is this necessary? Should I do that in addition to adding OM when I plant new stuff (blanket flower, clematis, balloon flower and creeping phlox for sure)?

Thank you so much for any help!