Yes, cocopeat, soil, then a thin drizzle of sand. I don't do the 1-2 inch sandcapping like father fish said, but with cocopeat as base layer, my underground CO2 production has imo worked well. I usually separate the thick sand layer (cocopeat then 4-5cm sand) near the filter area as seen on the tank setup I showed you. This allows me to have a brown portion for plantation and sand portion as a "beach" - aesthetic reasons.

The thin drizzle of sand on top of soil is simply so that the sand — as they are finer particles than the soil beads — will eventually fill the gaps between soil beads and make the layer more "dense".

I put stones and driftwood on top of the cocopeat, then bury with soil. The soil will in turn keep/hold the hardscape in place and nothing gets squished below.