CGMatter shows how to simulate material depth by setting up an array of textured layers and procedurally adding masking to them. The result is quite convincing and has much better performance than using displacement nodes. This technique works for both Eevee and Cycles.
The sound of this tutorial is a bit weird at points, but the content is well worth it.
I have a LONG history with Blender - I wrote some of the earliest Blender tutorials, worked for Not a Number and helped run the crowdfunding campaign that open sourced Blender (the first one on the internet!). I founded BlenderNation in 2006 and have been editing it every single day since then ;-) I also run the Blender Artists forum and I'm Head of Community at Sketchfab.
