I've been looking at S. subulata seed at all the various seed websites. They all say it takes a long time (up to a year) to germinate. Most instructions are to sow heavily, and cover very very lightly (the thickness of one seed). Jelitto says to sow them in a coldframe in the fall, for germination the following year. They also suggest starting them in a controlled climate condition, like indoors or in a greenhouse, and starting them in space thrift trays, to wait out the germination.

Outsidepride's instructions are on their website, linked below:

Here is a link that might be useful: Outsidepride Groundcover Instructions

I just planted my seeds a week ago, looking at no instructions, and just put them with some organic mix potting soil mixed with sand.

I checked this morning, after keeping them moist and in the garage, and there are thousands of teeny sprouts coming up! :D