replacing sod with rock garden

I want to replace a corner of my yard with a rock garden, mostly for sempervivum, maybe some sedum. Are there any pitfalls I should look out for? I'm mostly concerned with creating a situation where the level doesn't remain stable, and it all starts to sink into the ground. I'm not sure if that's a usual thing to happen when replacing sod with rocks (and some succulent soil & sand) but for whatever reason it's my main anxiety. We get a lot of rain here, if that's relevant at all. Is it as simple as digging up the sod and putting down a layer of pebbles (how many inches, I wonder?), and building up layers of rock/soil/sand from there? Or maybe bigger, heavier stones should be the first layer. I have a bunch of decent sized rocks from where I dug holes for my trees.

Sounds like a great idea!
I think that stones-sinking-in-the-ground-scenario greatly depends on the type of soil you have.
But even then...I personally would just go with the inspiration! Let the situation guide you and have fun!
Big stones under, great! Perhaps a big papa-boulder standing up as a guardian?
Create your own landscape art according to your insights and vision, you can always adjust it if and when you think it needs some further "guidance".
Perhaps make a little photo journal here in this thread of the process? Inspiring!

I appreciate the advice and enthusiasm, Nina. You're right, I'll go for it and feel it out. I don't keep a smart phone or digital camera, so a photo journal here is not really possible. Maybe down the line as it shapes up, I'll ask a neighbor to take a photo and email it to me, lol.