If you take a look online, you should be able to find specifications for a dry laid patio installation.
However, what you are proposing sounds about right. I am not familiar with CR 6, but I am assuming it is a type of crushed stone. Typically a crushed stone base is installed at the bottom, then sand is laid, then paving material. You can either lay the slate so that each piece butts up against each other, or you can leave some narrow spacing, ideally about 1/4". You can then fill these joints in with polymeric sand, which hardens.
1.5 inch slate sounds fine to me.
The only time slate might be slippery is after a rain. I wouldn't let that stop me if you like the stone.
I get a lot of questions about installations. Maybe I should post a drawing on my site.
I hope this was helpful. If you have any further questions, just post them here.
