You may have noticed that all Troll Caves look the same. Thus it is easy to build in it and around it and share the build. Careful placement can net you the same results. 

I've nudged the outer iron gate just outside of the (E)nter range for the cave. The inner gate is behind it. Not that it will fool anyone, but after you open the outer gate and try to open the inner one you enter the cave instead. 

Down below is a camouflaged portal with a chest on the other side to store Ore into in case you forgot and can't teleport. Also one a Ward to protect your build that you can reposition afterwards if you want to use the eyes as illumination that can be seen from the stairs down to it.

It is possible to use a beam that almost disappears into the cave opening and hang a Brazier inside one of the rock sides. This provides light as though from a hidden source as well as Comfort while you're there. 

You can dig the tunnel around to the right and behind the Portal to make a small room for a bed if you want, the Brazier acts as a Fire so you can rest. Just be careful not to dig too far or the ground above will shine through once you've dug past the edge of the Troll Cave feature. 

With all the hidden features (the fire out of sight/reach and the optional bed down stairs and around the corner) monsters won't attack it. Even shaking ground events result in the monsters just wandering around outside with nothing to do unless you engage.

I have other builds that use other existing caves for underground rooms that I'll post if this one is well received.