Need help with slate set up

[EldritchPreacher]

So as the title says I’m planning on using slate in my mature bearded dragons enclosure with excavator clay in between as I want a natural looking set up for her. My issue is getting large enough pieces and making sure they don’t get too hot under her basking light. Any advice?

 

[EldritchPreacher]

I want to make sure she’s safe and happy at the end of the day