Your thinking of the eastern boys and their jagd/teckle setups - couldn’t be further from that. That is not an artificial earth
artificial earth is actually dug into the earth, approx 1.5/2ft deep, minimum 2 entries/exits and one chamber
west facing, good drainage, water source nearby, on a slight slope, dog-leg angle on tunnels to minimise draft, chamber doesn’t have to be massive
tunnels lined with field stone and small slabs over the top (I put plastic feed bags over slabs Before filing in
chamber lined with breeze blocks and big old style concrete slab as top