I use about 65% organic soil, 20% ground up/shredded hay, and 15% shredded wood chips. Not sure if this is good or not but seems to work well enough, keep some humidity. I add a bit more soil incrementally...
I use cypress mulch and organic top soil. I would stay away from using any hay products, as this will mold with moisture. I set mine up with mulch on the left under the hot lights (dry side) and soil on the right under CHE for a humid side. All of mine tend to sleep on the humid side at night.
Here is my big enclosure, so you can see how it is set up:
pancakes love nothing better than to wedge themselves into rocky crevices. My enclosure now has plenty of rocky sheets and stacks, but a coir base. I had cypress mulch before, which also worked fine